well...as much as im a fan of all-motor.... i have to admit, n20 is a good bang-for-the-buck item.

keep in mind ANYTIME you force air into your motor, you're going to reduce its reliability. with that said:

i think a 55-shot would be ok, i wouldnt risk anything over that though. make sure you put in the right jets for the n20, my friend accidentally put 125 shot jets on his contour svt when he meant to put in 75 shot jets. needless to say he melted some pistons.

also keep make sure you have an adequate fuel system set up to take the n20, the last thing you want to do is run too lean. lean+n20=boom!

im not sure if a 55-shot would require a new fuel pump, but look into it first.