1990 troop with hesitation stumble=no answer

[sourgrout]

I have a 1990 with a 2.8l TBI I have done a major tune up and cleaned the throttle body inside and out. The truck has a slight hesistation from a stop and when I'm cruising down the road around 25-35 mph it jerks and stumbles. When I block the egr by plugging the vacuum line it goes away and she runs perfect. So I replaced the egr and tested the egr selenoid valve and it still does it. Its like its getting too much egr at lower rpms. It idles great with or without the egr plugged and if I stomp on it it has plenty of get up and no hesitation. just acts up when driving lightly. Anyone else have this same thing happen to them? How to fix? I cant figure it out...
Thanks

[Quyinnindenver]

Did you clean out the Egr tube as well when you changed the EGR Valve?

[sourgrout]

yeah I cleaned it out. The egr system works, but it effects the drivability too much, like the egr is giving the engine too much exhaust gas. I think it might be weak fuel injectors that are causing it although it runs great without the egr hooked up. so I dunno

[Quyinnindenver]

Have you done a pressure test on the injector rail?

[sourgrout]

Yeah 12psi at idle but drops to zero as soon as i turn the motor off. dunno if thats normal for a tbi

[Quyinnindenver]

yep 12.5 psi @ 1000 rpm and pressure should drop but down to 5 psi when the engine is off.

[sourgrout]

OK thanks, my other concern which was brought to my attention is that if the fuel injectors are weak or have a poor spray pattern, though it runs fine without the egr, when engaged it compounds the problem... i really dont want to make the mistake of dropping 200 bucks into new injectors if its not the problem so I'm alittle hesitant. The truck has 147k miles, I assume the injectors are stock. I did a TBI tune up kit and cleaned the crap out of it and sprayed and soaked the injector tips in injector cleaner... however they could still have a bad flow pattern. i tried to check em with a timing light pointed down the tbi at night, but I didnt see any conical spray pattern. Oh and the stumble gets worse as the motor warms up.Any other thoughts?
Thanks for your help

[Quyinnindenver]

dids you clean the injector rail? also did you run a round wire brush through the exhaust railshould be able to get one at home depot it should be 1/2 inch to 1 inch. with a foot long rod that will fit on the end of a drill.

[sourgrout]

this truck is a tbi it doesnt have a fuel rail..