[Alan Roehrich]

You can gain a pretty fair amount with just tuning, Ed is correct, the factory tune is abysmal. There are tunes that use the different grades of fuel. It's still a big block Chevy, it likes timing, and timing likes octane.

There are people gaining substantial additional power and fuel economy with headers and a free flowing exhaust.

There are a couple of people modifying the intake by removing a substantial restriction, some are adding a bigger throttle body, and killing the EGR, as well as relocating the PCV system, because the PCV system will literally suck oil out of the lifter valley.

The intake and exhaust work has shown another 30-50 HP, depending upon how much intake work is done, and depending upon your use and driving style, another 2-3 MPG. If you constantly use the added power, you won't help fuel economy at all.

I have been developing a bolt on adjustable rocker system, but it is on hold right now. The plan is to have both stock ratio rockers for those upgrading the camshaft but not replacing the pistons, and 1.8:1 rockers for those keeping the stock camshaft.