Can you modify the tune, I attached and disable the rear o2 sensors. Since ive installed an offroad H-Pipe.

I bought a used diablo sport predator (U7140) for my 05 v6 mustang, i just installed it with the 87 octane performance tune. the guy before had a custom for his C&L cai which is still
on there. Can i just change the Global MAF thing by 5% in the 87 octane tune ? I have a BBK CAI, Airaid Throttle ...