My first thought was spark plugs, but you said you changed them. What type did you through in there? Dual electrodes? Did you gap them properly, if they weren't pre-gapped (always good to check anyways).
Have you ever changed the fuel filter?
It could be so clogged, that when the engine is trying to get more fuel, it can't flow through it fast enough.
Same thing with dirty injectors.
My mechanic only charges $80-90 to diagnose vehicles. If you can't get it figured out, just take it somewhere, have them tell you what's wrong, and then decide if you want to do the fix yourself or not.