Re: dual ehxhaust
Wrong, because you lose velocity of the exhaust gasses in the pipes. The engine actually has to work harder to pump the exhaust out. There is a difference between a 3.0 V6 and a 502 big-block. The bigger pipe you use, or more pipes, the higher the rpm has to be before you see any benefit. If you look at, say, Gibson Exhaust's own data, you will see that their single system adds more torque and hp on a Ford V6 than their duals will. Same with a K&N on a small engine, you won't see a benefit until 4000 rpm or more. At normal street speeds the engine isn't flowing enough air that it matters. Although if someone wants to put duals on, then by all means go ahead. My suggestion in this case would be a single-in dual-out Flowmaster behind the cat and bend up some tailpipes. 2" pipe would be fine.
'05 Sport Trac 4x4, L/S, torsion lift, extended shackles, 265's
'03 Taurus wagon, Silverstars, Yoko TRZ's
If you give a man a fish, he'll eat for a day. If you teach a man to fish, he'll sit in a boat and drink beer all day.