So I recently played around with the idle screw, and turned it till I was sitting at around 850 RPM at idle (in accordance with what z32.wikispaces.com said). But now the car seems to shake at idle, almost like an old muscle car? Is the idle too low and I'm reading it wrong? Or is it something else? It isn't shaking a huge amount like it would if a cylinder was misfiring or something, but it is noticeable.