[91GTturbo]

You tend to see more driveability problems with 42's than 38's. Unless you have a custom chip or run some kind of fuel management system, 42's tend to foul plugs and are hard to get the car restarted once the motor is at operating temperature and they load up at idle. Some guys run them with the stock electronics and have no problems at all, depends on the car. With trying to decide between those two sizes, I say go for the 42's for just the added bit of safety and if it gives you an excuse to get a chip, at least your combo is optimized.

I don't really trust the analyzer, it said my 30's were fine and my car just dies after 4000 rpms. I bought a set of 36's, I've seen them with no fmu make a little over 420 rwhp.