yeah, too much boost actually takes away alot of power. the stock turbo is only good for 18-19psi anyhow. as mentioned, the S3 might get a little more since its a different turbo alltogether. the stock fuel system can only support about as much as the stock turbo is good for. pushing boost higher, you would probably also want to upgrade your fuel and add a return line, just to be safe. and as always a wideband to monitor your a/f

now, for the cost of the S3 you can get more power out of a non-mopar turbo kit. but then you also have to worry aboutkeeping it tuned, as well as buying various other stuff that will nickel and dime you. (wideband, fuel pump, return line...) the S3 you can just install and run. however, if your talking about getting the S3, its setup already. if your going to get S3, then put a different wga and use a mbc... you might as well just not get the S3 and go with a kit from like APG or something.