can be anything as far as the check engine light. but most likely a bad egr sensor. sometimes the o2 sensors go bad and can cause the car to dump fuel . that would make the car stumble off line.
check fuel pressure should be no more than 45 with the vacuum off. on a stock engine and 35 with the vacuum on. give or take 3 psi in either direction.
how the rest of the cars tune up??