I just picked up my 97 with GT2554, MS1.5PNP, DO methanol injection, Ford 400cc injectors in December and I'm finally getting around to trying to figure out what is causing the POP POP POP at high boost, near WOT. I noticed in the data log today that around 5000 RPM, WOT, the AFR jumps from around 12 to 17-19 and the RPMs wiggle. (don't know proper terminology) That's when the popping starts. I'm attaching some screenshots of the log, the raw log file, and the msq file. Any advice would be appreciated.

 

You're definitely running out of fuel at the top end, 12.8 is leaner then i'd run at 200 KPA.
Overboost protection on? Spark blowout? (what coils/plugs are you using)

 

Overboost protection is on but it did the exact same thing when I used a manual boost controller instead of the EBC. I don't know about spark blowout or what coils/plugs are in the car.

 

Wouldn't spark blow-out cause a rich condition? Not a lean condition?
Unburnt fuel going into exhaust would cause the pop-pop, but you'd read rich.
You seem to be leaning out quite a bit.

I may also be talking out of my ***, someone correct me if i'm off my rocker.

 

Misfires always show as a lean condition,

 

Can you help me understand that?
AFAIK, a misfire is caused by the spark not lighting the fuel, causing unburnt fuel to go into the exhaust. This would be picked up by the O2 sensor as too much fuel, causing a rich situation.
I'm not debating, but trying to comprehend why I'm wrong.

 

O2 sensor measures Oxygen content rather than fuel content. So it'll see the cylinder(s) full of air leaving the exhaust rather than the unburnt fuel

 

Thank you for clearing that up! Have a cat!

 

If I'm running out of fuel on the top end, is that something that can be resolved with a tune or will it require upgraded injectors? More than the 400cc ones I have now.

 

More injector AND more fuel pump. You're at 90%+ duty cycle near the top, which means your injectors are maxed out. If you're running the stock fuel pump I bet it's also near its limit. Especially if it's old.

 

According to the previous owner, it has a Walbro 255HP fuel pump.

 

How much boost are you running?
I'll be running 700cc injectors with a stock pump on stock wastegate pressure with a no electronics kit from FM (2560R)
Will I be running into the same issue?

concerned...

 

I'm running 14psi.