I have a 02 GT 5spd with 78k miles has diablochip,FIPKII,UPR X pipe,welded in flowmaster 40 series...one day i cranked up the car and the exhaust seemed like it was quieter with that i felt a loss in power what can I check....any ideas... i cant even scratch 2nd now :/....
Diablo Chip maybe? Any time you start messing with the computers in these things that is what happens IMO. My buddy has a chip (not sure what brand) but he'll say its runs great at one start up and then the next start up it runs like the flintstones. Kind of like your PC sometimes its fast and sometimes you want to throw it out the window. I may be dead wrong, just my opinion.
I bought the car with the chip on so ya...I dunno gas cap is tight... fuel filters been done yes it does feel slower.. could it be a dirty air filter lol?....
Check the connections on the intake for the PCV valve ect, and also you could have fouled a spark plug, if you haven't changed them in a while that could be it, I use NGK copper plugs, if you have a K&N or equivilent you can recharge it, I have a chip and never had a problem with power loss, another thing you can do is change the oil, I put some royal purple synthetic seemed to give some more power
Chips have been known to come loose. I'd suspect this or a hose that's loose - if it suddenly happened like this like you've said, it's likely something that is not working, as opposed to something that has deteriorated over time. With that said, if you haven't changed the fuel filter lately, chg it!