I had my p/s set done by OSROCKET just this past week. I specified a medium pinch, due to some wear of the conrod, but I'm cheap and didn't want to replace it yet. The engine is a Dynamite Mach 427.
The difference in pinch is very noticeable.
This is what I just emailed to them.....

I got my piston and sleeve back the other day and finally got around to installing it and the engine itself back into my tuck. I could tell the difference while playing with the set before dropping it in the case. I richened the high speed about 3 hours, and the low about 5. I didn't need a hair dryer on the head, even though the temps are in the 50's here. Maybe the spin start helped there.
After it fired up, I immediately noticed a higher idle, though I could tell it was pretty fat.
I figured it'd need the ignitor on it to keep it running. After about 2 minutes I decided to do some slow figure 8's in the street, so took the ignitor off to avoid damaging it or the plug. After a few more minutes the rx battery died, so I brought it back in and let it sit in the driveway.
I bought the truck used, and I haven't had a nitro vehicle in over 20 years, so didn't really have a baseline to go on and was surprised at what happened next. Previous to the pinch, it would die at idle within 5 seconds, every time, no matter the tune. With the pinched sleeve, it sat in the driveway, fat and happy at 178 degrees, dripping oil all over the place, for almost 10 minutes without me touching it. I shut it down and put the piston at BDC for it to cool until the next round. I can't wait to lean it back out. I can already see the potential, and the need to tighten the slipper on my LST2.

Best $22 I've spent on this truck. Thanks John

Andy