plz help - turbo muffler on N/A (future plans for FI)

hey guys i'm really sorry to keep bothering ya'll with this... i got the apexi N1 universal muffler (for N/A with 90mm and small ass canister). first impression when i saw it installed is that it looked too small. now i look everyday and now i wish i got the turbo version (the muffler that comes with the full catback) at least... or the whole catback instead but too late now.

i'm thinkin of takin it back , changing it for the turbo one (115mm tip and bigger canister), but one problem, it comes with an 80mm inlet.

would this cause any problems being welded onto my existing custom 2.25" catback piping?

what would be the affect on sound?

thanks guys