Limp mode or boost leak?

[Satummoo]

I got my car chipped a few months ago, then went on vacation and it doesn't feel that fast anymore. After driving a few months I definently have confirmed it just isn't what is used to be.

I've been running with a CEL on, code: P1426 which is for the Evap canister (don't know how to fix, I tried the gas cap thing)

I had it cleared for codes at autozone and it still isn't boosting right. Should I try disconnecting the battery? If so, should I disconnect the positive or negative?

Thanks

EDIT: I should note, the CEL was there when I bought the car, I knew what it was
The ECU is a A-box flashed to an M-box - It was amazing when I first installed it
After coming back, it didn't seem as peppy, I replaced the TBB and both diverter valves