hey guys, hoping some of you can help me out with possibly a stupid mistake I made. I recently swapped out my tranny and did a timing belt job on the s4. Well now once everything is back together the car wont start. It cranks for a second or 2 but then cuts off like its either out of juice, or its getting an opposing fire in the cylinders. when i stop cranking it lets out a small backfire.

battery is fine
I kept the stock clutch and flywheel in the car, they were not touched
kept old vss and cps
when i remove the crankps, it cranks just fine
when I remove the cam position sensors it still has the issue
if i pull the number 29 fuse( engine timing i think) it cranks fine
My ICM's are new

I've gone over all of my connections and they all seem to be in place. I'm wondeing if my ECU maybe went bad, APR hardchip, or I've read that the vss can go bad. Another possible thing is maybe I'm missing a ground somewhere. I have 3 grounds hooked up by the ECU on the firewall and one right there connected to the block of the car. Can anyone check their car real quick to make sure I have the correct number hooked up to the firewall?

Also, for some reason I feel like I may have turned the crank an extra 360 degrees. I would hope I'm smarter than that but could that cause this problem. I didn't hear any valves hit at all while cranking it though. I'm sure the timing belt isn't off any teeth. I replaced the spark plugs with NGK ones that autozone called for and gapped them correctly during the swap as well.

I haven't been able to get my hands on a vag to test any codes yet but I'll try to today. The car ran like a dream before I swapped the tranny.

please help get the only nogaro left in louisville back on the road :(