Still have problems. Car starts hard cold, 2-3 5 second cranks to get going. No stumble/hesitation once started, but after 10 minutes, get the stumble/hesitation off/on, but defininately get it on a hard right turn. Here's the list of things done:
New Control Pressure Regulator
New Crank Sensor
New fuel filter
new FI relay
Checked/swapped radio surpression relay
Removed/cleaned Throttle body
Removed/set up throttle position switch
Pulled tank pump- new filter, good bellows hose, pump seems good
Pulled main fuel pump- seems ok, check valve seems ok
ran Chevron Techron FI cleaner through system

Any ideas? Got to get this hesitation problem fixed by March- Daughter starts driving ;(

Bob

I had a bad stumble on hard acceleration. It turned out the air hose from the Air Mass Meter to the throttle body had been pushed off the AMM and was just sitting pressed against the outlet of the AMM. When The engine torqued over, the hose at the AMM would move a little away from the AMM giving a bad vacuum leak and making the engine lose power and stumble. When I looked at the air hoses, they looked to be tight. Maybe you have a similar problem and the engine moves on a hard right turn and opens up a vacuum leak.

replace the plugs, bosch or ngk-no platinums, and check the cap, rotor and wires. replace with bosch only except wires, those only oe or bougicord. check the output from the mass meter. check the bellows from the mass meter the intake for cracks. you replaced the fuel pressure reg-control? pressure, that's kjet, you have lh 2.4-but, what is the pressure? good luck, chuck.