I am posting this for a friend from the other forum..

99l, 12lbs boost, CAI, FTVB, predator, et streets.

So I went to the track, and did my burnout in second gear, I forgot to shift back into drive and hit the limiter. I quickly shifted back into drive and all was well.

The next run I did a much larger burnout and launched with a new best 60' time of 1.8 however the truck lost power at the top of first gear and never recovered down the track. ( had about a 1/16th of a tank) At first I thought it was just the boost bypass, so I cleared all the codes in the predator and reloaded the factory program.

Now the truck idles rough at first with a very lean AFR 18-19:1. It then slowly richens to 14.7:1 after a few seconds and smooths right out as normal. When driving there is NO power and any throttle causes the AFR to go very lean and the truck stumbles badly. From 0- 1/16th throttle the truck is fine, anything over that and it seems like its just not getting any fuel.

My thoughts..
Burnt plug? But it still idles perfect when the AFR is right.
Low Fuel pressure? Any way to check this?

I am at a loss here, anything else to check in the predator??

 

sounds like one of the lines on the fuel pumps in the tank has poped off. common on 99 trucks

 

Something similar happened to me at the track.

Do you see your boost gauge moving at all?
In my case it was the vacuum hose that is on the drivers side of the engine.
Its towards the front of the engine kinda aligned with the TB on the lower right side.
Its hard to describe where its at, but its the only one down there if i remember correctly. Mine popped off but when you look at it it seems as if though its on, but it isnt.

I lost power going down the track, had rough idle, no power at all, fuel pressure wouldnt budge and my boost gauge wouldnt budge either.

 

As said commom prob for a fuel line to pull off inside the tank
BUT
Dont rule out plugs

A bad plug WILL cause a lean condition, actually it'll look that way on screen, but it's really not.

and will sometimes run perfect up to a certain RPM or MPH, depending on how the plug is damaged.

This has happen to me numerous times, and yes the truck will sometimes idle great or be fine at light pedal

 

Boost dump. Are you doing any type of boost bypass? If not at high RPM the boost dump solenoid will bleed off your boost. Shut if off for a few seconds and restart. All is well. Disconnect the boost dump solenoid. Driver side at the rear of the blower.

 

It was the line going to the pump in the tank. 6 new clamps and the truck is as good as new. THANKS for everyones help.