I saw a comment about 1.5-2psi at idle??? No it sits in vacuum. It has a bypass valve that creates NO boost at idle or very light throttle. The valve shuts when you want the power and believe me its instant. when cruising at light throttle boost will sit at 10-20psi of vacuum, then when you hit the throttle its an instant 6-8 psi depending on what pulley you are running and the overall flow of your engine. Also engine rpms play a role in boost psi as it is belt drivin. From merging onto the highway under 1/2 - 3/4 throttle I may see 3psi of boost up to 5 or 6 and if I stay in the gas to redline it will peak at 10psi.
My opinion about the JRSC in general is very good. I have hardly ever popped the hood to make sure everything was up to snuff. Basicaly bolt it on, tune it and forget about it. I'm using a cartek FMU with an adjustable rising rate ratio up to 15:1. It works very good much better than the JR IMO and have been running stock injectors for about 30k miles now. So far so good.
The down side like we all know is upgrading. I knew this when I bought it and really didnt feel the need for more boost on my B7 as it cant handle it anyways. You can always do the option of water/alcohol injection seeing as you cant intercool it. My next build will definatly be turbo, high boost, and a complete build including sleeves and a little bore

This project will take tons of time and wads of cash so in the meantime the SC is perfect for me. 37mpg on the highway, power on demand and pretty much worry free. I'm sure power gains on a Z6 will be much better than my puny B7 but what can you compare it to? Well, at the 1/8 mile track its about .1 quicker than a stock GT mustang. Thats not much but then again...its only a 1.5 non vtec. Did I mention the engine has 230k miles on it and blows smoke hehehe. Hope that helps you make a decision.