what about with exhaust 3"
turboback sys

 

You're right foot has the biggest effect on fuel economy. I wouldn't count on seeing too much a change when you upgrade to a 3".

 

If you go catless, it should be the same fuel economy, if not better. The reason being is that you are unclogging the exhaust system of cats and allowing the car to breathe better, putting less strain on the engine and all of its components. Sure, it will be easier to boost and that might affect you alittle, but not much. As stated above, your right foot is the best fuel regulator. Even if you're staying catted, it should be around the same. Better breathing=better fuel economy.

 

so really it doesnt make a big difference it makes it better. Anyone know the horse power gain on 3in. exhaust HKS hyper no cat w/ up pipe

 

i have a question:
what are the differences between running cat less or with cats, pros can cons?

 

well i think the main one is that with no cat you get the most horse power gain. Cause the car breath a lot easier.

 

I'm running the 3" Vishnu turbo back w/ a high flow cat.

Pros:
no stink
evironmentally friendly
quieter
"less illegal" than catless

cons:
~10 less whp
cat will eventually clog/break apart
heavier
more expensive

I happy with mine b/c I commute, and I need a comfortable exhaust system. If you are looking for all out performance catless is the way to go.