Since you do dyno every change, how much horsepower were the underdrive pulleys worth? Which pulleys did you switch?I'd opt for 60hp heads or something before I went to anyone's aftermarket computer, myself. A VEC2 will give you good gains for 1/3 the price. /images/graemlins/smiles
Problem with Vipers is they are a speed density system, and any major flow improvements like a set of heads cant be compensated for by the factory system. Meaning if you have a set of heads giving you 60hp your car is now running extreemly out of tune, and may be prone to detonation. Not to mention the fact that if you gained 60rwhp from those heads untuned the gains after tuning would be major.I understand the point, but I know someone personally who gained 80hp from his last dyno run after adding expensive ported heads and rockers; with no tuning. He didn't have any VECs to tune with. Vipers are known to be rich at WOT as set from the factory aren't they? Then there'd be some additional richness already there waiting for additional air. Add in the fact that the heads improve flow downstream of the injectors, there may be enough improvement in wet flow to add to the total. The ported heads aid exhaust flow as well of course, Just as Belanger headers would add a substantial amount to pre-creampuff engines with no additional tuning, it is possible to extract hidden HP without further tuning. Though subsequent tuning would surely be worth the trip... /images/graemlins/smiles
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