car dies during decel when pushed

[No Mercy]

1990 turbo. Just got it. Havnt even done a tune up on it yet. 10k on new motor but was rebuilt/installed by an amatuer my bro found a ton of bolts missing and wires unplugged whenhe scanned over it. I flushed all the fluids put new pads n rotors and a new battery and rrplaced o ring on the crank pos sensor. since ive gotten it...so i really havnt been driving it much becuz it needs some lookin over/work before i know how reliable it is..i mostly go to the corner store for diapers. However....
i have gotten a lil curious and dropped the hammer a few times..did a few 3 rd gear drops on highway and a few 2nd rolls and a few digs maybe 10 times combined ive romped on it....EVERYTIME it feels great..i mean the car runs good....but then when i throw it in N and press brakes it dies...now since im rolling i just toss it in gear and push start it to keep it movin and then slow all the way down and its fine....a few times it died during the decel for like...1 second and just came right back to life without me doin nething. This ONLY happens when im into the throttle 3/5ths or more and normally if i slowly roll into it it wont even happen. Like i said tho it ONLY happens in neutral tho. When im in the gears on the throttle it runs amazing. Im not mechanic i just dabble...my bro has been doin all my work for me for 11 years...but hes been so busy he hasnt had a chance to check it all out. I decided maybe i can pick you supra pros brains a bit maybe u can point me in the right direction. Let me kno if u need ne more info on the car.
Thanks for your help and time!

 

[kotu100]

Really sounds like a boost leak of some sort.
Check engine light on? If so pull the codes. Could be the AFM acting up.

 

[No Mercy]

Check engine light is on. Havnt checked it yet cuz ive been lazy but ya i thought it was an exhaust leak but there was nothin noticable at first glance but boost leak sounds reasonable cuz i really havnt checked it out dont know my way around turbo stuff yet still very green to forced air. Thanks for input thatll move to top of my list when i get under the hood on a day thats not like 100°.

 

[A-to-the-J]

Do you have an aftermarket BOV?

 

[No Mercy]

No its the stock BOV

 

[radiod]

Yeah, I'd check for boost leaks first. Make sure the recirc hose is all hooked up and not leaking off the BOV as well, it's very typical for it to go rich and stall when doing exactly what you described when that's leaking. Take a quick search for DIY boost leak tester and you'll find how to make one super cheap and easy, then all you need is access to an air compressor and you're good to go.