I have read 2 1/4" diameter will support 400 hp. Any idea on how much power might be lost going to 2" diameter duals.
2 inch will be much lighter, leave more room and allow the use of quieter mufflers!
Personal preference, I wouldn't put 2" on anything but a slant 6. Now saying that, a 2" dual system on a stock 318 is probably borderline overkill but, unless it has mandrel bent pipes, the bends are restricted down to 1 1/2" or maybe less.
