My exhaust is a single pipe then it splits into dual from the muffler. Does that ADTR inatke fit a 3800 series 1 ? Do you know anyone that make headers? I would like to gain as much power as I can without tearing down the motor.

We are pretty confident it will fit on Willwren'* car. Headers for Series I does not exsist. There are not much part'* for a Series I N/A because the engine only have so much potential until you replace it w/ Series II parts.

How big is the single pipe?

-Hector

The single pipe I believe is the same as the bonneville. I think its 2.5 in.

IF you want a little more bolt on power, all you have left to go is an intake, switch up your Flowmaster for a better flowing muffler like a Magnaflow and cleaning up your exhaust manifolds, welding it on the outside to get a little more radius inside. Then to gain more power you have to go inside the engine.