i have the 4" DIY icebox on my gsr and I love it. Im not sure on the differences between the 3 and the 4 but i dont think they are noticable to the butt dyno
Yes the ecu does learn after a few drives.. Well i have the 4" incher diy on my ls, i just have to put on my horn at the end that i bought at pep boys. It's a 3 inch hole, but the horn is like 5 or 6 inches.