[200q20v] Mixture....advice needed

[Brian.Link at Level3.com]

If I have already asked this question then sorry for the repeat.
I need your opinions,  What would cause my car to run lean from about 6psi
up to where I hit the point where I trip the computer to go full rich.  
I've been through Scott M's web site and I think it might be either a vacuum
leak or a bad fuel regulator.

No error codes stored.
New throttle position sensor.
New BV
New fuel filter
recent techron treatment.
new vacuum tubes from BV to IM, from fuel regulator to IM, breather hoses
are soft but solid.

I installed an autometer Air/fuel gauge and I feel this slight stumble when
it goes lean but no missing or stumbling, the car doesn't fall on its face.

could be bad fuel regulator, Is there a place to hook up a fuel pressure
gauge tot he rail?
Could my TAP chip have bad fuel table mapping...not very likely.
I have supposedly different then stock injectors, RevSport installed RC
injectors..I don't now what size.
Vacuum leaks, where is the best place to check.
fuel pump going south?

any advice on my problem is appreciated.  In fact I would have never known I
had a problem if I didn't install that gauge.  Stupid gauge

thanks

Brian Link