The car I have is a 1998 Buick Regal GS
Its supercharged and the tensioner on the front of the 3.8 SII went bad on me. The racket was awful and the car quit running (acted like it flooded out). I located the problem purchsed a replacement tensioner hooked everything back up now the car will not start and the engine almost feels unbalanced.

The car turns-over fine. (cranks)
Is it possible that the timing is off?
What might be the cause of the no start now that the tensioner is replaced.
I have double checked the belt pattern and it is correct.
I checked and the service engine soon light stays on after the ignition is turned on.
This is the same result both with and without the belt.

Thanks
--B98

Double check that you didn't accidentally disconnect or pinch any wires (like the ones that go the crank position sensor) when changing the tensioner. I would also suggest getting the car scanned to see what tripped the check engine light.