[IUP99snake]

As one of you pointed out, the D1SC is a better unit, with steeper internal gearing and an upgraded impeller. Thereby, making more boost more efficiently than a P1 without having to go to a smaller pulley.

But the biggest limitation with the P1 (and even the D1) is with the belt setup. They run off the factory 6 rib serpentine belt. This creates inconsistent boost during heavy fluctuations in RPM, and increases the risk of throwing belts.

I've had my P1SC making upwards of 15-16 PSI. However, I've made 510RWHP on only 10PSI with a powerpipe and exhaust.

The P1SC will support upwards of 500 HP if the motor is tuned correctly and no bottlenecks are present (powerpipe, good exhaust, good tune, etc). You can easily increase this by going with an 8-RIB conversion (which should be done regardless).

The D1 is an impressive little upgrade. My friend Brian with a Red 01 cobra (who resides on these boards) installed a D1 head unit on a nearly identical engine combination as mine made 569 WHP on 12LBS of boost (when I made 510 on 10LBS of boost). Both engines had stock internals at the time.

While I'm happy with my P1 combination because I have stock aviator internals with 10.5:1 compression, and don't plan on pushing any more boost. Since you already have the P1 head unit, there are a few things you can do before you get something else.

1: Power Pipe (this will give you a few extra LBS of booost)
2. Blower-Brace (reduces belt slip and flex)
3. 8-Rib Conversion (or even a dedicated conversion). Since the blower case is the same size as the larger D1 or F1, you can upgrade the bracketry now and see how much of an improvement you get. There was a neat article in 5.0 mustang about a dedicated blower belt drive that significantly increased horsepower with the same blower and pulley sizes.
4. Once you have addressed the aforementioned supporting issues, only then would I upgrade the head unit. You could upgrade the impeller to D1 status for $1200, but you might as well just go balls to the wall with an F1 if you have the supporting mods.

Homer