My 97 has a 270 hp plate and a K+N air filter. To retain similar fuel mileage and more jam would I want 4" exhaust and then maybe injectors ?

 

Lose the K&N filter... Fuel mileage shouldn't be affected by the fuel plate. Just your right foot. The fuel plate only lets you fuel past the stock governed amount at different rpms. Exhaust would be a great next mod. 5" sounds a little deeper, but 4" is all you need.

 

I have had the plate for 7 years and no it didn't hurt the econemy but what do I need for more power that wont hurt the fuel mileage when I'm being good ?

 

Why lose the K+N airr filter ? Is there any draw backs to 5" exhaust over the 4" ?