[V8] Stumbling / surging problem

[David Lyddall]

Has anyone come across a problem like this one:

 

I have a black '90 V8q auto, and when it's cold, it drives like it is
running out of gas.  It idles fine, but at partial throttle it really feels
like it's starving of fuel.  When it does this, you can floor it and it will
get up and go, although it feels a little short on power.

 

Here's the list of things I've tried - I double checked that the timing is
correct - it was off a couple of teeth on the cams, but it is fine now.  It
has a new fuel pump - the old one was wining like crazy, but that wasn't the
problem.

 

It feels like a bad mass air flow meter - bogging down under partial
throttle, but I switched the one out of my other V8q and it made no
difference.  Also tried switching the TPS, but made no change either.

 

It has a fairly new oxygen sensor, so I think that is unlikely to be the
problem.

 

Before I got the car it had sat for about 3 years, so the fuel system was
full of varnish.  It does have a new fuel filter, but I wonder if maybe the
fuel pressure regulator is causing trouble.

 

Any ideas would be appreciated - I really would like to make this car run
right.  I've been using it as a loaner car at my shop, and it gets old
explaining to people what they need to do when it dies on them.

 

Thanks

 

Dave

 

90 v8q x2

96 a6w