Regarding your car not being able to burn out, the first thing I would recommend is the "fuse pull":
http://www.camaro5.com/forums/showthread.php?t=38964
In regards to the "intermittent knock sometimes at startup", it may possibly be the AFM lifters that need to be replaced. A quick search for "L99 lifter tick" will yield the following:
http://www.camaro5.com/forums/search...rchid=13634028