Knowing what California is like, it probably isn't street legal unless the company paid the big fee to have it tested and Cali emissions approved.
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2005 V6Mustang coupe. Automatic. Black with Charcoal Interior
Mods: JLT CAI, Bamachips 91 race tune, single Mustang V8 muffler, Mustang V8 swaybars
Looks: smoke front turn signals, sequential taillights, 14" shorty antenna, MRT rear window louvers and a little chrome for the interior 2000 C5 Corvette convertible, Torch Red with Black Interior. Full of options, Corsa exhaust 1990 Ford Bronco 351ci engine- it runs.
Does everything that affects the drivetrain have to be CARB-approved?
Not sure, but because the heads affect combustion I would assume that they'd fall under it. Whew! Glad I live in Colorado where as long as your car doesn't fog the road so bad that other drivers can't see, you're cool.
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2005 V6Mustang coupe. Automatic. Black with Charcoal Interior
Mods: JLT CAI, Bamachips 91 race tune, single Mustang V8 muffler, Mustang V8 swaybars
Looks: smoke front turn signals, sequential taillights, 14" shorty antenna, MRT rear window louvers and a little chrome for the interior 2000 C5 Corvette convertible, Torch Red with Black Interior. Full of options, Corsa exhaust 1990 Ford Bronco 351ci engine- it runs.
There's dyno sheets on the supersix website. The hp gains are okay but the lower end torque gains are huge. The downside is the cost. With the cost of installation tacked on it'll probably be about the same as if you'd just gone out and gotten a supercharger.
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2005 V6Mustang coupe. Automatic. Black with Charcoal Interior
Mods: JLT CAI, Bamachips 91 race tune, single Mustang V8 muffler, Mustang V8 swaybars
Looks: smoke front turn signals, sequential taillights, 14" shorty antenna, MRT rear window louvers and a little chrome for the interior 2000 C5 Corvette convertible, Torch Red with Black Interior. Full of options, Corsa exhaust 1990 Ford Bronco 351ci engine- it runs.
It should be more. Super Six has a reputation for good hp gains with all of their parts. The packages for the OHV engines produce very nice gains and the OHC motor usually gains better than the OHV engines do so I do not see why you would not see some nice gains out of the package. Super Six has not put as much time/effort into the 4.0L as it has the 3.8/3.9/4.2/4.3 though so that could also be a reason.
Go to their website and look at the dyno sheet. It's on the left hand side about halfway down and it's in pdf format. Here's what they say at the end:
'4.0 SOHC Mustang, automatic transmission, single exhaust, Stage 2+ cylinder heads, gained 25 peak RWHP and 19 ft-lbs RWTQ with non-peak gains of up to 50 RWHP and 80 ft-lbs RWTQ with no tuning changes on a Mustang chassis dyno. 5-speeds will net higher gains, and even higher gains are anticipated with tuning changes.'
If you look at the sheet you can see that down in the lower rpm ranges you gain massive amounts of torque and that's right where you want it.
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2005 V6Mustang coupe. Automatic. Black with Charcoal Interior
Mods: JLT CAI, Bamachips 91 race tune, single Mustang V8 muffler, Mustang V8 swaybars
Looks: smoke front turn signals, sequential taillights, 14" shorty antenna, MRT rear window louvers and a little chrome for the interior 2000 C5 Corvette convertible, Torch Red with Black Interior. Full of options, Corsa exhaust 1990 Ford Bronco 351ci engine- it runs.
Super Six Motor Sports 
