Hey Waterboy, welcome to GS. Nice car
(Tell us a bit more about it - and maybe fill out your
garage.)
Exhaust: freer-flowing exhaust has been discussed much, but nobody's found anything conclusive for mpg one way or the other. I don't believe anyone's done a trial on the subject.
One problem with doing a cat-ectomy (aside from the obvious) is it will cause the computer to throw a Check Engine Light (CEL) when the rear O2 sensor detects elevated emissions.
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