2003Evo

no way you should be sacrificing 7mpg with your power level. No cats and a big cam will definitely make the smell worse, but combine these two with a super rich a/f ratio then you will most likely suffocate from the exhaust fumes.
I have no cats on mine and in cold/chill weather I can def smell my exhaust due to cold temp fuel enrichment. Once the system gets nice and hot then the smell goes away. In your case your fuel enrichment is so bad that its making the car undrivable. Get the tune checked asap.

Highroller101

Well turns out I've been chasing the wrong thing.

I have been leaking oil on the headers and this is what I was smelling.

Moto One

Even though you found an oil leak, check to see if the PO didn't cut any holes in the trunk area. Possible route for fowl air to enter.


Mark

Sam Handwich

I don't think that is why the mpg is so lousy.
good luck with the rest of the problem.

Fast one

Are the exhaust manifold gaskets new and not reused even once?

striper

Even though you found the source of your smell problem, what about the horrendous mpg's you have been getting? You seem to still have a problem.

Highroller101

I drove 85 miles on the highway to a performance shop last week and averaged 75mph getting a total trip avg of 19.3 mpg (city and highway combined). Part of my problem is I have a hot cam that doesn't like to be below 2k rpm. So around town I'm driving in 3rd gear sucking up gas. The highway I was driving in 5th at 60-65mph. At 70mph in 6th I'm at about 1800 rpm and it's good. I was getting 23mpg when doing 85mph but I don't need or want a speeding ticket.