With the single port you won't see as much as the split port. Exhaust may give you Hp but if ur piping is to big you will lose tq.
Get a CIA, exhaust, and tuner and you'll have a decent difference. Big gain for our sixxers is an 8.8 rear with t-lok and gears, no added hp/tq but better acceleration.
If you want lots of bug power on a six, like 250-300rw. Or even 300 crank, you'll need forged internals and some sort or power adder.