HELP!! car stalls and dies when decelerating..HELP!!!

[Slowbra94]

I am really stumped about what is going on with my car...ok these are the mods the car came with.. its a 94 cobra: flowmasters, chip ( i have yet to find out what kind), a hoemade CAI w/ a pro-m 80mm maf, and all else stock that has to do with performance... the problem started after i replaced the maf from the old one ( i do not know the size), however, prior to the problem, the EGR was no longer hooked up to the main harness. The previous owner disconnected everything that has to do with emissions: the smog pump is gone, the tube connected the EGR to the header was cut and welded shot, the EGR regulator is missing. At first i tried to replace everything, but after taking it to the shop, and finding out the connection to the main harness was cut ( the one that leads from the regulator) i just plugged all the holes leading to the EGR. Also, there were exhaust leaks coming from the passenger side header and a tube that was left open which i could only assume used to connect to the smog pump. By the way, i live on FL. so there is no emissions, there is no need to worry about this. Anyways... after replacing the MAF which i thought was an easy task, i took the car for a test drive, there was instantly a noticeable difference in performance but slowing down was where the problem lies. The car accelerates better than before, the problem is when the car is reving over 2,500k and then then placed to neutral or i try to down shift, the rpm's drop dramatically below 600k and will die, i can keep it alive by steppin on the gas. ALso i have notice that if i keep the car in a lower gear while slowing down, it will stay alive. I have read almost all the posts before posting this thread.. and the closest thing i found was a problem with the TFI coil. but that cant be since i recently replaced the TFI coil with msd, changed the plugs no more than 2 months ago, and along with the new MSD TFI i also replaced the FMS 9mm wires with the same thing... what in the world would cause this ridiculous and annoying problem?? by the way the reason for my changing MAF's was because after running the codes on the comp, found out that the MAF was malfunctioning. EGR has always been blocked off so that cant be it either, the header leak was fixed, all exhaust leaks were taken care of! also, before the header leak was fixed, the car used to back fire when decelerating... now it does not backfire anymore, this all happened after replacing the MAF.... i called Fordanderson, and they checked everything on their records for my order and it was correct ... 80mm maf for 24lb injectors. pls help!!! and sorry for the insanely long post!