Spark or fuel?

[Mr. T-Type]

I finally fixed every problem with my car except one which I can't seem to put my finger on. Found 4 vaccuum leaks, a bad MAF sensor and a bad TPS.

The car is idling correctly, not hesitating when I gas it, and not losing all power after 10psi.

However, if I go WOT, the car will overboost (I'm supposed to be on stock boost which I'm told is 15psi) past 15psi and then gasp and lose all power. I can hold go about 66-75% throttle and build it up all the way to 15psi (around 4000-4200 rpm). Anything higher than that will cause it to overboost and gasp.

I don't want to throw parts at it and I don't know anyone with coilpacks I can borrow. Can anyone help me diagnose this? I'm throwing my Walbro 307 on tomorrow night in hopes that the stock fuel pump is what is holding me back but I highly doubt that.

Only mods are 36# injectors, 2.5" downpipe, and Duttweiler necks.

 

[Roger]

I recommend the "Y" hose to the turbo & a complete spring cleanup.

 

[blackbuick87]

Originally posted by Mr. T-Type
I'm throwing my Walbro 307 on tomorrow night in hopes that the stock fuel pump is what is holding me back but I highly doubt that.

The stock fuel pump is most certainly out of breath after 15psi. Do you have a scan tool? With a stock FP and overboost you could be very well be experiencing high Knock Retard which is causing you to lose a ton of power

 

[WarpSpeed]

Could be fuel pump, but that wouldn't explain the high boost.

I'd take a close look at the wastegate rubber hoses for leaks/plugs, and the actuator for a blown diaphragm.

 

[6=8]

Sounds like my problem... After fixing various problems, I was overboosting. Found the replacement "Y" had too small of a restrictor/orifice... Check out this site:

http://www.johnsperformance.com

I purchased the orifice listed for my GN and it worked great! I have never been happier with the way my GN runs now! Finally, after all my work, it was this inexpensive part that got everything to work!

Now Instead of buying the special "Y" I can just get the ones at the auto parts store and thread this little thing in.