I've had both an SE and SVT Y & main cat on my car. The pipes are the same as far as I could tell. I got a good close look at both, but I never actually measured because there appeared to be no noticable difference in the pipe sizes. I'll put a calliper across the pipe at my flange if somebody would be willing to do the same for an SVT - then we'll know for sure, once & for all. We gotta measure the pipe going into the flange because of the different flanges - the piping is what counts anyway.
My stock SE Y pipe has a 3 bolt flange, the SVT unit had the spring loaded 2 bolt flange thingie that mated up to the converter pipe.
I sold the SVT pipe & cat system & kept my modded Y pipe. I like it.
