vividracing

The fact that you've only got 1000 miles in the last year means the car has sat quite a bit. Old gas can cause issues like you described. So can "bad" gas, like ^^^ said. Start by reading the trouble codes and see what that says. I'll bet it's a misfire or MAF sensor code. It could also be the CAS, but unless you have issues starting the car then I don't think it's that. Diagnosing this is going to require some knowledge of how the ECU works and which sensors do what. If you don't want to learn (and possibly buy tools) then take it whoever installed the SC kit. If that's not an option, find a local shop that works on performance cars. If you can find someone that knows Nissans, you're in even better luck.

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