Question:
What is the ideal exhaust set up for our rigs to gain more torque and/or horse power from the stock 2.0 engine?

2" exhaust or 2 1/4" exhaust 2 1/2" exhaust?
2 cats, 1 cat, no cats?
OE muffler, High flow muffler, duel muffler or no muffler?
Single exhaust or dual exhaust?
Stock diameter to second cat, larger diameter after?
Larger diameter pipe from 1st cat to tips end?

Is it even worth the $$$ to change the exhaust, or is there no gains?

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2002 4dr Kia Sportage 4X4
Tires:235/75/15, Wheels: Black 15x8 Steel ProComp 2.5" B.S., Hubs:Warn Manual, Lift:3" UPYOURKIA, Trailer Hitch, Cargo Rack, Clinometer.