I am helping out my mom.
She just bought a 2001 PT Cruiser with an aftermarket supercharger and aftermarket manual 5-speed installed (she got totally taken advantage of at the dealership but that's another story).
It drove fine for about 100 miles when it was driven on the freeway up from Southern California to where my mom lives, but has now started to stutter when I switch gears, almost like it's not getting enough gas, but it still has a quarter tank. The speedometer also starts going haywire when it starts to stutter.
I took it into a repair shop and they said they didn't get any error codes when they scanned the engine and didn't see anything wrong with it, and they suspected it had something to do with the supercharger, but they won't touch it since it's an aftermarket part. I've called around to several shops locally and they all say the same thing, that it's probably the supercharger but they won't work on a car with aftermarket parts.
According to my mom the dealer showed her a way to unplug the supercharger so she can get it to pass SMOG inspection in CA, but of course she doesn't remember what he showed her. I'm trying to figure out if I can just unplug it and my mom can still drive it around.