Car is a lsx 427 with a billet 106 with Fast XFI as management system. Recently had some trans issues and finally got everything back together and decided to do some trans brake testing and tuning with the new Griner 1-2 leave option valve body. This past sunday I went out and fired the car up in the shop and let it warm up and then proceeded to test the car on the brake. First started in 1st gear, normal routine..... Foot brake the car to about 3200 then grab the brake and let it climb to the 2 step set point which was 4000. Everything worked great so moved the limiter on up to 4200 where it normally is. Again everything worked flawless. Continued to do this 5 more times in first and then did the second gear testing and same result. No issues and it build rpm and boost as it should. Move ahead four days to last night (thur) and the car hadnt been touched at all( I mean nothing) all i did was add a quart of trans fluid and then started testing the brake for final tuning adjustments for the track tonight but the car will not come up on the brake at all. Same routine, foot brake til 3-3200 and then grab the brake and the rpms start to come up by then act sluggish and never reaches the two step limit no matter what. Ive lowered it all the way down to 3200 and it will reach it then but also does what Im about to tell you next. As Im on the brake and building boost and rpm the car reaches about 3550-3700 and then falls flat on its face no matter what we do. Every log is the same, I will be at 100% throttle and rpms will start falling while im still wide open and will be for another .5-1.0 then I will lift off the gas. In this time frame rpms drop about 3-400 every time. Car has never done anything like this and nothing has changed. Not one thing!