u can still run pump gas having a higher compression...maybe not 15:1 but if you ran 12:1 lets say you could use 93 octane. Even if it was just 11:1 (stock ITR ratio? maybe its 11.5) thats a significant amount of power believe it or not. With a p&p job,good valve train, proper tuning and of course good intake and exhaust..13's would be the be the least of your worries...id start looking into buying slicks =P