Re: Anyone experienced changing to the performance pulley on the SC
I would personally go with just a tune, from a good reputable tuner(look for jag tuners) before going with a pulley.
An overdriven SC pulley will increase spin rate, and therefor will increase boost, however the engine was not designed for this, and I don't mean in the way of the increased pressure. The SC on this engine has also been a cause of concern when it comes to reliability, so making it spin faster might not really be in your best interests.
By increasing spin rate you are also increasing air temperature, which is not accounted for in stock form, the intercoolers are not designed to dissipate more heat then the stock setup produces. You are also not really increasing air flow nearly as much as you would think, the increase in manifold boost level is more so due to the restriction of air through the intake ports, as again, it has been designed for what it is. Keep in mind, this SC set up(from pulley to intake port) was designed for what the cylinder head flow, you will not see much more usable power from it without creating more boost with more airflow, not the other way around.
The 600hp set ups are not lies, but its not exactly the same as a ~100hp gain. In increasing intake air temp, you loose combustion efficiency, which at lower engine speeds will be noticeable. It is the whole peak vs area under the curve argument for anyone that has ever been into performance engines.
The reason I say go with a tune before anything else is, this same essential engine, with the same SC and pulley on it, has different variants, with huge power differences based mostly off tune, although minor changes to intake and exhaust(post SC, and pre cat - you will see almost nothing but noise gain for a cold air/K&N, or cat back setup) But take the Jag XF, the XF SC is rated at 470/424, the XFR is rated 510/461, and the XFR-S is rated 550/502. All of those have the same base 5.0 that you have, with the same Eaton TVS1900 blower.
If a new tune (and do not get some mail order thing, those usually do more harm then good) does not satisfy, look into a performance shop, and upgrading the base blower from the TVS1900 to the TVS2300. This would give you more flow at the same spin rate, and a lower air temp. The intake restriction element would still be there, so it would not be entirely ideal, however it would be a much better option. To put this swap in real world application terms, it is really the main difference between the LSA engine in the Cadillac CTS-V and the LS9 engine in the Corvette ZR1, with rated outputs of 556/551 and 638/604 respectively.
