mrpeanut1983

We swapped out a stock LS1 in an 01 trans am too a stroked LS1 from an 04 G8 and had it dyno and tuned dyno says it is making 591HP at the flywheel but when we ran it at the track it performed the same as the stock motor and sounds like it has a miss and is backfiring once off the gas and even started doing it in the pits but on the diagnostics it doesn't register a misfire or show a dead cylinder. We think there may be an electrical issue but are looking for any ideas on what might be causing this lack of power to the back and the car running rough and sounding like it may be dropping a cylinder while driving.

G Atsma

Could it be starving for fuel under acceleration due to fuel moving from the pickup?

mrpeanut1983

it has 64lbs of fuel pressure and the AFR was tuned too 12.6 so it shouldn't be starving plus it still sounds off at an idle

Austin_Jim

Check the grounds. Battery to frame, battery to body, body to frame, frame to engine. In my Chevelle, I was having a bunch of weird things happening like the tranny slipping, funkiness in my gauges, etc. Usually after the car warmed up. Turns out my ground inside the vehicle wasn't great. Once I put a new grounding post behind the dash that I connected to the frame, everything started working well.

Old Buzzard

Not an LS1. It's a gen 4 6.0 with AFM.
Way too much info missing to avoid a lot of guessing, throwing money at it.
What ecm are you using? A "swap" harness?
Start by posting the pertinent info, the tune file and data log of the issue.