What else can I check besides fuel pump and relay, all done, when the computer says nothing is wrong?

 

If it's a Turbo you can check the intercooler hoses...

 

you could have gotten a really bad batch of gas. This would cause the computer to retard the spark and degrade performace.

 

Could be a bad o2sensor,massflow sensor,Plug wires, ETC

 

I had some power loss problems for a while. Turned out it was just a bad connection with the MAF plug. cleaned it up real good w. dye electrical grease and reconnected it and it was all good. The guy that had the car before me doubled the wire over and ziptied it. WHat a dumbass

 

The funny thing is it wasn't the guy before you it was the dealer.
There is a service bulletin to do that.

 

Damn, that's crazy. Well that was the problem and after removing that, it worked fine. You never know