I need help! I know the post looks long but its a pretty bad problem.
So i am about to replace my cat convertors, and if the timing is off it might lead to early failure in the new cats. So i checked the timing and it ws at like 2* BTDC so i went by the book on making it 6* BTDC and double and triple checked it, and yes i unplugged the est bypass connector while doing it.So i took it out for a test drive and it was quite a slingshot of a ride. then i drove to school about 10 mins on the freeway. I noticed a pretty heavy knock only on when i hit the gas or if i was goin uphill. so i took it home and checked it again and it was at 12* BTDC so i retarded itback and drove it back to school and it was fine. on my way back it was the knocking again. so i looked at the timing again and it was perfect at 6*.

What have i done??? did i miss something? i even thought it could have been the ****ty gas i put in even though it was still 91 octane. so i burned up the remaining 1/4 tank and added the 76 stations finest rocket fuel and added octane booster and noticed nothing.
Any ideas are greatly apprecieated. Im going to check my header boltstomorrow.
thanks

 

ok the header bolts are fine. ive heard if the exhjaust is grounded somehow it can cause the engine to spark?
anything guys?