Would deleting my 2nd cats and installing a true dual h-pipe get me better mpg?

 

Whatever you do, I'd keep cats on the car. I've been catted and catless and you get a much betterr sound with cats. I've had a custom dual exhaust setup on my car and I couldn't say for sure if it got better or worse mgp over stock, but I didn't have a problem hitting 30mpg on long highway runs. I'd recommend going with 2.5" exhaust if you are having it made.

 

Some guys take of just the secondary cats. Apparently those are really restrictive.
It's after oxygen sensor so won't really mess anything up.

Did you take of primary and secondary? Or just secondary?

 

well the 3IS is a true dual iirc and it's MPG numbers are comparable to the 2IS,

 

I have headers so my primary cats have been gone for a while. I had a pair of magnaflow cats installed when I had my dual exhaust made which was about half the cost of the system. I am currently catless due to one of the cats failing from hitting speed bumps due to me being lowered. So far my peak maf values are not really any better or worse than they were when catted so I would say that there is no performance hit from having the cats and the difference in sound quality makes it very much worth the cost of the cats.