Brian puts up some important info here as does the last poster (totomacher). Lots of variables affect the final performance:

1.) Boost Pressure - more usually means more power

2.) SC'er drive parasitic losses. The SC is matched to the speeds and flow requirements. As we overdrive it the SC performance is moved out of the sweetspot. This causes parasitic losses to drive the compressor to go up at a near exponential rate. A 185 pulley causes that loss to be up to nearly 60hp off of the crank hp the engine is making. What it means is that while the 185 makes more boost and thus more power, proportionately less is getting to the rear wheels. That don't mean it makes less rwhp only that the law of diminishing returns is starting to kick in. While the 185 may only increase the overdrive of the SC by 4% compared to the 178 pulley or the C3P unit, the increase in parasitic losse increases at a rate higher than 4%. I am not going to quote the actual SC loss as I do not have the charts in front of me but it is out there for those who want it. If I remember right, I think it is about 45-50hp for the 178/CP3 option?? guessing on this. Maybe someboday has it? Bottomline is more overdrive means more power but less of it is useable power to the wheels with a SC'ed engine using the same supercharger.

3.) IAT - will be different everyday and at every altitude but all things being equal, it will goe up with boost pressure. Unless measures are taken to improve the cooling of the intake air (intercooler, IC pump, cold air to filter, etc) then more heat robs some of the benefits from the higher pressure.

4.) Mean effective pressure - this is the combination of Intake pressue and compression ratio. The engine cares little where it comes from. Lower altitude=more pressure, as does higher compression pistons or more boost from SC'er or Turbocharger, etc. Each time you double the mean effective pressure, you double the torque output at the crank as long as you don't do something dumb like run out of fuel flow to compensate for the extra O2 and then go too lean causing preignition (knock) and then causeing the ECU to pull timing.

5.) DA (Density Altitude) and formal way to express atmospheric pressure and air temperature in pilot terms. Basics are more atmospheric pressure and lower air temps = more horsepower all things being equal. If your run the same car at Englishtown in NJ and then run it at Mile High in Denver with same temps at both, I guarantee that it will be slower in Denver.

6.) Fuel injector, pump and fuel rail flow limits. This is a big ??? with our cars. At some effective flow level, we will hit the wall on this without making changes. All the turbo car tuners know this. That is one of the reasons why the 185 pulley piggybacked to the Code3 pulley failed to put up more power.

7.) Octane limits of the combustion chamber design. Our cars run a 3 valve two plug system. That is a trade-off that give good low end torque, decent efficiency and fair resistance to knock at high compression ratios. It is usually not as good as a 4-valve cosworth style combustion chamber with a single plug in the center or a 5 valve Yamaha style design. No matter what type is used at some combo of fuel air ratio and mean effective pressure and at a given octane (say 93) you hit the wall. We cannot alter the design of the engine. We can only increase the FAR so much and without going to higher octane you are done.

8.) Octane limits of the fuel - Assuming that all fuels are equal is wrong. the USA 93 octane fuel is a chemical soup of so many hydrocarbons and additives that even on a given day from the same retailer and from the same refinery, it will vary all over the place. Winter vs Summer blends also vary. If the guy running the 181 pulley happens to have better gas and the guy with the 185 gets a tank full of crap and starts pulling timing, then the other fellow will post a better time. Not saying that the 185 won't be faster all things being equal, but the 185 pulley is closer to the ragged edge of the limits and so is more likely to be adversely affected by any of the variables such as fuel quality, IAT, DA, and boost pressure.

I personnally think that the 185 pulley is knocking (pun intended, lol) in the limits of the engine's fuel flow, ECU compensation range, octane limits at a given IAT and thus is giving some drivers erratic results sometimes. Your results may vary depending on where you live, the altitude, typical ambiaent temps and the quality of your local gas. I think that the guys who are in hot and/or higher altitude places will be able to run the higher boost with fewer issues than say guys in places where the DA is lower most of the time. Just my 2 cents...

Irish

PS. Look at our ole buddy jturkle from the C32 world. His 185 pulley is working for him. But being in the Phoenix area, the altitude is about 1100 ft above sea level and I hear that it does get fairly warm there sometimes which further increases the DA making it possible to overdrive the SC'er slightly more without over boosting the engine. Keep in mind that the engine does not know where it is or high high up. It only responds to the mean effective pressure and that will be less at higher alts and higher temps. Now take a guy at sea level in Miami, FL or worse, Long Island, NY, he could see issues sooner unless a custom ECU tune is applied to compensate for the conditions.