help with tahoe problems

i have a 2000 z 71 tahoe , just had the trans rebuilt now 100 miles later it runs like crap !!! my fuel presure is 48 psi at idle and when engine is shut off the presure drops instantly ? is this a pump problem or the fuel regulator ??

you did mention the year and model, so that is better than many, but a couple more bits of info would be handy, such as what motor it has, and what the actual symptoms that concern you are "runs like crap" is very vague

As a general rule, fuel pressure shouldn't drop "instantly", but if the residual valve fails, for example, that is more likely to cause long cranking starts, not runnability problems

Sounds like you may have an injector that is stuck open. If the spark plugs are not too bad to remove, perform the key on, engine off fuel rail priming a couple of times, then pull the plugs and see if you have one that's wet with fuel. If so, the injector for that cylinder is probably open and relieving the pressure from the fuel rail into the cylinder. That could be an injector issue or a wiring issue to the injector. The flooded spark plug probably is not able to burn the extremely rich mixture, so your engine has a misfire which would explain the poor performance.

-Rod

pull the vacuum hose from the regulator if any fuel is there then hold your cards we have a bingo