Yes this is my problem; but at WOT the car pulls hard with no miss. It is only at light throttle, going down the highway and accelerating at 70+ mph is fine.

I tested my fuel pressure today and found I have 40psi at idle and 48psi at idle with the vacuum line off of the regulator. The pressure is not bleeding off when I shut the key off. I am half tempted to buy a stock pump and remove my walbro 255lph pump, but the pressure seems to be good.

 

Lite thrpttle misses are often an indication of a small vacuum leak.

 

Henry, maybe we can answer this question together (I don't want to hijack your thread by any means, but we seem to have the exact same problem). I notice a hissing noise coming from my driver side of the engine as soon as I start the car. It continues until I shut it off. Do you have any hissing noises when you start your engine, too?

And if this is the case, Maddog, whereabouts would this leak most likely be?

 

Sounds like you may have a vacuum leak. I am just going to keep my car as it is; I have checked for vacuum leaks, and triple checked the ignition system. It really is not bad it just bugs me because I know it is there. Most people that ride in the car say I am crazy, but I know it should run smoother.

 

Yeah, and people told me the same thing until it got worse, then I knew I wasn't crazy... Lol... But yeah, I'll inspect that before I change the opti.

 

Places to look or listen for vacuum leaks: rubber elbow (bellows-soft rubber-prone to tears and mis-alignments.)
anywhere along air passageway to the throttle body intake
rubber hoses that should not hiss
A vacuum gage is helpful here.

 

I would check your o2 sensors also, I have the same problem with my car w/65k miles on it and I changed opti, coil, wires, plugs, etc and the car still has a slight miss at idle. It is very fustrating putting all that money and time into the car and nothing changes. Im going to try and unhook my o2's and see if that makes any difference, I doubt it but its worth a try. And among other things I started my car up last week after sitting all winter and the car has a high rpm miss pass 5k rpm now and I have a hard time believing its the opti because its an Delphi stock replacement with less that 2k miles on it. Im starting to despise these LT1s