1989 turbo need help!

[ftwmotorsports]

I joined this site to try and find some answers to a puzzle that can not be figured out. As by the name i am a Tech from a shop in Wichita,KS and I have a customers car here in the shop with a issue I cannot figure out. The car starts and drives pretty good but the only issue is when you try to make boost of any sort and let off, it will just die, unless you feather the gas a little. It had the tendency to go rich under boost, then extremely lean after letting off to the point where it would die. There has been several vacuum leaks found and fixed thinking that would solve the problem, but nothing. The codes were pulled and it came up with a code 51, which from read dealt with a couple things mainly being the tps which there was some wires found to be messed up and also it wasnt adjusted correctly. Now after playing with it some more there was a couple more codes that came up but that was due to playing with the maf. Now just so I am clear the 51 code has went away since fixing the tps issue. If anyone has any clue as to what is going on and a way to fix it would be greatly appreciated.

Thanks in advance,
FTWMotorsports