I've had one nagging issue with my 7427 MAF, 4L60E equipped 86 C10, it will not rev past ~4800 rpm, or exactly 35 MPH in first gear. It acts like it hits a fuel cut off barrier. Every "Fuel Cut Off" I can find in the parameter tree that is RPM related is set to 5500. I swore I found a 4L60E 1st gear parameter the other night that was fuel cut off related that was set at 35MPH, but I either dreamed it, or was drinking, because I haven't found anything like that again. I'm using the standard v251.xdf file to look at the 4L60E parameters. It doesn't shift into 2nd, it just hits the wall and starts doing an off/on surge, but it will not go beyond 35MPH in first. I haven't wound it out in 2nd to see if it repeats in that gear. I never hit a fuel cutoff in Drive due to the C10's aero dynamics, the 305 doesn't have the steam to pull much past 4000, and by that time the speedometer has gone past the 85MPH it stops at.

I was planning on swapping the 3.42s out for 3.73s or 4.10s, but would like to find this issue first before really impacting the trucks ability to wind out.
Thanks