If you already have a 3.5" Dp a full 3.5" exhaust would be best. I assume you have a larger turbo than stock, so you will be able to reallytake advantage of the larger piping. Yes 3.5" will be loud, it isnt quite as loud on a 1jz as they dont have as deep of an exhaust note as the 7m which does tend to drone at about 2200-2600 rpm. A resonator will make it quieter.........a bit. I run a full BIC 3.5" DP, TP , Thundercat back on my 1jz and it sounds perfect!!!.