To quote myself:
My friend the Racer Who Has Contacts Throughout The Industry said he discussed dual vs. single exhaust on Ford V6 engines with an engineer who did much of the exhaust development work for Ford. The engineer said the expense and effort required to equip a Ford V6 with a working dual exhaust system was far in excess of the value of benefits accrued; there were some measurable but small gains in high-end power, but not enough to warrant the investment on a performance basis. A well-designed single exhaust did nearly as much. Speaking of a stock or lightly-modified engine. I conclude that installing dual exhaust on a S197 V6 Mustang is an aesthetic matter, not a practical one; that is, if you like the look, feel, and sound, duals is good. I like ''em, they look good, some of them sound good, they make a lot of difference how I feel driving a car, but until those considerations become more important to me than better handling or proven performance enhancement like Cold Air Induction and a Tune, I''ll stick with a single (GT takeoff). I view that as a practical solution, at present. And it doesn''t sound all that bad, either:
single GT takeoff road test
single GT takeoff dyno test
Now I have the FRPP V6 duals. Very good. I like the stereo sound back there, and I like knowing it is a symmetrical appearance with the two pipes. Fourteen eighth-mile drag passes failed to demonstrate any substantial performance improvement, but ...
Yeah, it was worth it, although if I hadn't got Mr Bush's rebate that I wanted to throw away, I'd not have done it.
(One good thing about the FRPP V6 conversion kit M-5230-V6 is that everything fits, it's completely bolt-on with a couple of hacksaw cuts required, any able-bodied amateur can do it within a few hours, some in as little as an hour-and-a-half, they say.)
(Expensive? Hey, there's one kit out there that lists at $1,199!)
FRPP exhaust part 0ne (after the drags)
FRPP exhaust part 2
FRPP Exhaust Duals Worth the Money? 
