Quote Originally Posted by BiLL|z0r
I always thought a 2.25" was the ideal size for a 1.8ltr anyway. I doubt you'll notice any difference, maybe even gain some torque down low. You could the the exhaust fitter to slightly widen the 2.25" muffler inlet and shink the 2.5" outlet (if they can do that) so it's more graduale which would be best for air flow.
2.5" system is too big for a non turbo engine

2.25" is fine, as stated above u wont lose power, u may gain some torque, but dont get ur hopes up

im not sure, but i dont think changing the inlet to 2.25" is goin to affect noise level too much, it will be less, but i dont think itll be a significant drop

and u can pik up some generic rear muff with a 2.25" inlet for $300 installed