I am running a Super Hybrid K24 from Nick Knight, and I ended up running into boost fade issues above 20 PSI. Considering that I will probably end up closer to 30 PSI when the tune is done, Rob Hilton recommended upgrading the wastegate to a universal Turbosmart IWG75, PN TS-0681-5142. According to Nick, I probably could have gotten there on the stock WG with more preload, but I ended up needing to buy something from a company to avoid a restocking fee on something I was returning, so why not? I know Forge makes one for the K24, but apparently it can bind and cause issues, so I set about figuring out how to make the TS work.
UPDATE 9/13/2020: I have been told of another TS part number, TS-0620-2142, which looks like it will work better. It has a 140mm rod, which will be (barely) long enough, and it already has the correct thread, M6x1.0. It looks like the mounting studs are a little different on that one, so if you go that route, do your own measurements before drilling the bracket.
The first step is to remove the stock WG actuator. I did not take any photos of this process, but it is not too bad if you have a 10mm ratcheting wrench. Pull the OTE pipe and turbo heat shield, disconnect the vacuum line, loosen the jam nut on the turbo side and unscrew the adjuster, then it is just 2 bolts holding the bracket to the turbo. They are a bit tough to access, the ratcheting wrench makes this much easier.
Here are the stock WG and Turbosmart:
Note: the rod on the Turbosmart can be rotated, so don't worry about getting the orientation of the bends to the bracket exactly right like I did (which is why you can see a scribe mark on the bracket in some pics).
I took some measurements, first the stock WG:
Bracket is 5.25mm thick where the WG actuator attaches
Rod is threaded M6 x 1.0
51mm from mounting surface to the first bend
86mm from mounting surface to the second bend
98mm from mounting surface to the base of the threads
136mm from mounting surface to the end of the rod
Rod is threaded 1/4"-28 (weird, considering it is an Australian company)
100mm from mounting surface to the base of the threads
150mm from mounting surface to the end of the rod
Mounting studs are 6.25mm in diameter and 34mm apart
To start, I wanted to get the TS shaft to match the stocker. I determined that I could try to bend the TS shaft and then re-thread it, or I could cut the rod off of the stocker and weld it to the TS. I figured that bending/threading would be easier...but fate had different ideas (DUN DUN DUUUUUUUUUUNNNNN...).
I marked the TS shaft at 51mm, clamped it in a rag-covered vice right at that mark, and smacked it with a 4lb mini-sledge as close to the vice as possible until it matched the first bend on the stocker.
Then I marked the shaft at 86mm (this was still from the mounting surface; because of that first bend it is actually something like 89mm along the shaft) and bent it in the opposite direction. NOTE: *It is critical that the 2 bends are made in the same plane. Be very careful when clamping to get it right.
Then it was simply a matter of re-threading the shaft with an M6x1.0 die...or so I thought. Perhaps it was because the 1/4" threads interfered with the die, or more likely because I was using a POS Harbor Freight die set, the threads would not form properly and every time I went over them, the die removed more material. It also left weird variations in the thread, so nuts would not spin smoothly over them. Much cursing ensued because I thought that I was in the home stretch.
So, on to Plan B. I lopped off the ruined shaft of the TS @ 45mm from the mounting surface. I did the same on the stocker and welded them together using, of all things, a Harbor Freight welder. Be sure to mask off the mounting threads and the threads of the rod to prevent weld splatter from adhering. I didn't do this, but luckily, I was able to remove the splatter without messing up the threads too badly. Also, clamp the shaft with a meaty set of vice grips near the mounting surface so you have a place for the ground clamp and to serve as a heat sink. Dunk the rod in water between welds to keep it from getting too hot, otherwise you could ruin the actuator. Also, don't weld on a plastic table. I was being dumb and lazy.
Now, a quick note on the importance of shaft length (tee hee!): The stocker uses quite a lot of preload on the WG arm, meaning the adjuster threads on to the rod much further than when the WG first seats. The TS is only installed with 2mm of preload. I made my shaft the same length as stock, and it does not thread all the way through the adjuster on the turbo. The adjuster is 10mm wide and I am only getting about 7mm of thread engagement when the TS is preloaded in accordance with the instructions. I am pretty sure that is enough to hold without issue, but I would feel better if the adjuster was fully engaged. Regardless of which method you use, you should aim to have the final shaft length of at least 140mm. If you use the bending method, I am not sure if you will need to trim the tip of the shaft at all. The WG arm on the turbo has some room for thread past the adjuster, but if you don't trim the shaft it might bottom out in there before the WG seats, which will prevent you from building boost properly. You probably don't need to trim it, as my bent shaft (tee hee!) ended up being about 147mm, but I can't tell you for sure.
Now you need to attach the TS to the bracket from the stocker. I used a cutoff wheel and grinder to remove the stock actuator from the bracket and get a nice, flat surface. Then I drilled the holes for mounting the TS centered on the hole for the rod. After that, it was a quick splash of paint on the exposed steel of the actuator rod and the bracket and 2 nuts to complete the assembly.
After that, it installs just like the stocker came out, with the previously noted exception of setting the preload. You can rotate the shaft to get the bends in the right orientation by grabbing it with vice-grips. To properly set preload, thread on the adjuster until the WG seats and you cannot turn it any further. Then make a mark with a sharpie at the 12 o'clock position on the adjuster. Apply pressure to the WG actuator until the WG lifts off of the seat, then thread the adjuster further on the shaft by exactly 2 full turns. Tighten the jam nut and you are done!
Here is a pic with the actuator at rest, followed by one with pressure applied to the actuator showing that it moves the WG without binding.
Having executed both methods of modifying the shaft, I would probably say that welding was easier and faster than bending the rod, which took quite a bit of careful precision and checking the bends against the stocker to get them just right. If you are going to attempt the bending method, I recommend you start by re-threading the shaft since I don't know if mine got screwed up by the cheap tools or because the 1/4" threads interfered with the die. You can always fall back to the welding method if you need to. This took me ~6 hours, but that includes all of the photos, measurements, and having to execute both shaft modification methods. I would probably expect this to take the average mechanic ~2-4 hours with this guide.