I honestly dont think its engine internals because if you're afr hasnt changed or your boost level hasnt changed and no smoke, no noise and nothing at all, then might not be engine problem. IF it was a loud bang from the front of the car and you are positive it was from front, then check under the car, you coulda have hit something or maybe something snapped. And i think OP would know what a backfire sounds like. He doesnt sound that dumb. lol

 

underpanel connecting piece could have snapped. also are you open dump WG?

 

or maybe as simple as something on the street that got kicked up into the engine bay or hitting oil pan etc... like inner tire pinching a rock n launching it.

 

When you let off the throttle did you push the clutch in? I'd say one of 2 things happened 1. the clutch disc threw a puck or 2 engine had a mild burp (explosion inside intake manifold).

 

Yes I had have push the clutch in while letting off the throttle. explosion inside intake manifold is it something that I should be worried about???

Thank you.

Good idea, but I just changed my oil like 50 miles ago.

Will do sir. Might be able to do it this weekend when I go to PA. If I see something out of place I will thake pix.

 

I would just bet on running something over... if you've been boosting for 2 years now with no issues, and it ran just fine afterwards, with all the same specs... then you probably just ran something over. as someone else stated, running over a rock with the inside of the tire popping the rock up... will have a rather metallic bang to it as well.

 

I'd at least look at the throttle body, the manifold is pretty beefy if there was a problem you would know it. If it were anything else you'd feel a problem such as a vibration, noise or leakage somewhere.
Pushing a boosted "stock" engine to redline can be catastrophic. To do that safely you really need better valve springs, stronger rods and pistons let alone better clutch/flywheel.