you might get 10-15 hp with both. nothing to write home about. i have the kkm with a custom fmaster exhaust. a definite increase and if you stay off the gas you might see a few more miles per tank. think about it like this though the faster the air goes in the more gas it burns but supposedly you are making the engine work less and it stays cooler with the exhaust but when you stomp it you loose all the gas savings. before kkm 320 miles a tank (around town average) after kkm 335 average. before exhaust with kkm 335 after 345 at best, without any wheeling and driving more conservative than before. one thing i noticed is that my highway mileage is less at higher speeds. i might get 320 mpt at 75 mph but i will 345 at 60 mph (a lot of road trips have afforded me the opportunity to test this thouroughly.)
go to 4lo.com it has a bunch of awesome calculators for hp and such based on time speed weight. you can time your 1/4 mile runs before and after and figure roughly how much hp gain you have.
good luck!
