408 intake backfire issue help!
 

Ok I have a brand new 408 in a 2000 Trans am. I'm not super good with hpt yet so I figured I'd have a shop tune it to ensure it is done right.

So the car started and ran pretty good, then sat for about a week and the shop said the car ran out of gas. Now with fresh gas the car runs HORRIBLE! It is backfiring through the intake manifold as well as the exhaust. Any tips or tricks? I'm going there today. I should be able to get the tune as well if that would help. What can cause this short of a dropped valve, bad timing or a bend push rod? Should I pull timing and data log everything? I don't even want to have it running in this condition. I'll post up videos, cam specs, and tune hopefully later today.

This project is killing me.