SSMonty is right.
Sounds like a number of things it could be.
Have u check fuel pressure before and after the regulator? The regulator is built into the tbi unit in the back. Rebuild kits are cheap for them. This is a common side effect of the spring being bad. I would start there.
Problem is probably in the TBI unit, maybe injectors..
Intake coolant temp sensor. Especially since it seems to doit once its warmed up. EGR could be clogged. Bad MAP. Bad cats, Maybe? It could be any number of things.