got a question on MAX power

[TRD StreetRacing]

as i was looking through the dyno list cuz i'm interested in buying a exhaust....i saw some ppl got a max power of around 175 w/ a injen and trd exhaust and some ppl got the same thing w/ a intake and no muffler.......and some ppl got a max power of 171 w/ only a intake.......how is this possible? is there not that much of a gain w/ a exhaust? 500$ worth it? the only differences was that millage on each car......does the milage mean NEthing?

[NoCones]

ever heard of random variation?

you'd probably see variation of 5-6 hp across bone-stock cars dyno'd back-to-back

you'd probably see variation of a couple hp with the same car on back-to-back runs.