Help!!!

ok, i have a 96 grand prix 3.1. i am looking for the correct firing order. my car is dead! i mean it runs, but under any acceleration, she bogs out real bad. it is so weird, so i will tell you the symptons.

1) rod knock, and lifter rattle
2) poor acceleration, if any
3) when you mash the pedal, the RPM gauge goes nuts. seems to be slipping???? :eek7:

any ways, this is the first time i have ever encountered this type of problem. i added half a bottle of STP fuel injector cleaner w/ 10g of gas. since then my car has damn near crapped the bed. i have also changed the spark plugs. i do believe i put them back in the same order, but hey, ya never know. :banghead: there is a CEL on, so i took it back to the garage whetre he told me it was the cap?????

So if anyone can tell me possibly what the problem could be, and what the firing is on my car, i would appreciate it very much.