160 vvc making 143 power

So I'm on my second ZR 160 and recently had it rolled where it made 120 at the wheels, this was on a stock exhaust system and enclosed air filter (without a cold air feed was just resting in the lower half of the airbox)

My previous made 115 at the wheels with same intake but janspeed backbox although i dont think it lost power because of the janspeed before anyone takes it that way



Keep seeing people quoting 170-175hp but is that because other peoples vvc are making higher stock figures or just decent modifications push it from 145 to 170?



Spend more time around 306 gti6 cars and they generally hold their stock power even on higher mileages it seems,so is the k series just a sucker for loosing power over time?

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