I dont know how i got there on youtube but i did. Turned out a pretty educated video in thanks to a comment below it bu a GM certified mechanic w/over 30yrs of experience, which said "This happens due to a leaking fuel pressure regulator. Fuel line pressure leaks into the plastic upper intake plenum through the vacuum line connected between the regulator and the plenum. When the engine is cranked ignition spark ignites the large volume of fuel that has leaked into the plenum causing a huge explosion. There is not a recall for this condition to my knowledge. I am a Master Technician and have worked in GM Dealerships for 30 years. Replace your fuel regulator."
check this video to see what he is talking about, trust me you wont regret it, specially those of you who have regular 3.8 with plastic manifolts!

Yea, I seen that on here somewhere before.