WTF? FP drop on 2nd & 3rd gear and OK on 4th & 5th gear during boost. Help!

[SupraClaou]

When I am on boost I got lean conditions like 13-14:1 on the AEM wideband
during 2nd & 3rd gear pulls.... FP drops 0.3 - 0.4 bar from the desired 3.6 bar .
And during 4th and 5th gear pulls I got a normal 11.2-11.5 : 1 on the AEM wideband
and the normal FP of 3.6-3.7 bar.
For example,when I boost from 4K rpm I got a raise on the FP at 3.4-3.5 bar and
after about 5K rpms it goes down at 3.1-3.2 and it alters my A/F numbers and
it gets 'Lean' .....

I boost 1 bar (14psi) of boost. I checked all vacuum hoses,fuel lines. No leaks.
I run 2x walbros GSS 341 High performance pumps and they are 6 months old.
Changed them when the previous walbros failed on me,but then I barely had
a fuel pressure raise on possitive boost....which was a 100% fuel pump issue.

What is going on here...it drives me crazy. I wanna re map the AEM with the tuner
on 22-24 psi of boost and right now I have to fix this issue before raising boost to
higher levels.

Is it an AEM/mapping issue? or a fuel pump issue ?
Anybody ever experienced something like that? :1zhelp:

Any help would be nice.I consider ordering some New Walbros ... :naughty:

 

[destrux]

Have you checked your voltage at the pumps while the problem was occurring? Could be wiring that's got a bad connection somewhere and the more violent acceleration in the lower gears is shaking the wiring more and causing a voltage drop.

Also, have you tried filling the tank up to full? Could be a starvation issue. The car will slosh the fuel alot more in lower gears. Could be moving the fuel away from the pickup if the tank isn't full enough. Running twin pumps probably puts one of them outside of the fuel baffle in the tank (I assume... I have never dealt with a twin pump hanger, I've always used a large external pump instead of twin in tank pumps).

 

[SupraClaou]

True is,that I have a very bad battery and I jump started the car with the help of another vehicle....But since
it started and the alternator was doing it's job thought everything was ok. On my voltmeter I had 12.5 V.
You think it might be a 'power' issue to my pumps,since they work on electric power?

Fuel tank was 2/5,almost on the halfway... But both pumps are inside the fuel baffle in the tank. Quite tight,but they fit!