[SOLVED] Boost hits, car falls on its face?

I'm a bit stumped with this one,
Taking a look at a first gen speed3 just did a basic refresh on it (loss of compression in cylinder 1&4) since we started it up its been running a bit rough, idling low, revving slowly. hpfp pressure under about half throttle is jumping up to 1800ish psi. Car is loading up and even hit 18psi under no load free revving in neutral. I can slowly rev it up, however, once it starts seeing positive pressure boost builds rapidly, fuel pressure jumps, car adds fuel, and it just falls on its face. Pretty lost as to where else to go, timing is fine, all connections are good, did a backpressure test seemed to be fine. any ideas? again, none of this is driving, this is all neutral. Car isnt good to drive at the moment.

 

People often forget to hook up the MAP sensor, kinda hidden under the intake manny.

 

double and triple checked it, that was one of the first things that popped into my head, thinking it could be a clogged cat, has a high flow cat on it so i will pull that off and check it.

 

Did you stuff any paper towels or rags in the turbo, piping, intake etc to keep stuff out and forget to take it out? Seen this happen.

 

Nah, had the whole head taken off including manifolds/turbo. Havent gotten a chance to get the cat out and take a look at it, if it isnt that then I will be at a loss. hopefully it doesnt give too much of a hard time.

 

Sounds like the cat to me especially if all the other stuff that @Gandalf was mentioning was checked.

 

How could it be the cat if it was running before with the cat?

 

Injector issues maybe? AFRs normal?

 

Yeah what do your datalogs of this happening look like? Can you upload some?

 

found the issue, timing was off just a tiny bit, corrected it, runs great now! @neganox i would have thought it was the injectors but we had put new ones in when we did the work. Looks like this one was my bad! lol. Thanks though guys, I was starting to run out of ideas!

 

Just curious... but what made you originally think the timing was fine in your first post?

 

May be silly, but boost lines connected to the correct ports/right order? Also, make sure a line isn't pinched shut.

Falling on face is probably ECU's intervention when it sees the dramatic overboost.

 

He's already solved it, it was the timing.

 

possibly my own ignorance. lol.
[doublepost=1458073719][/doublepost]Yes I got it figured out, thanks everyone for contributing. I was at a loss there for a while.