I took a gamble and drilled my stock pipes. No regrets so far. There's a slightly better sound and better punch, feels more aggressive.The asthmatic whistle persists and I put this down to a) the stock can's small exit diameters and/or b) the gas flow through the cats.
There are two baffle plates approx 1"ish apart, I only meant to drill one but, well you know
. I also joined a series of holes so have an irregular shape, I'm going to try a hole-saw to improve this. I've contemplated doing the same to the end plate then I could adapt my own baffles.
So far the only intake mod is a stock air vent on the L) side of the air-box (got the right, just have to drill & stick it)...haven't even gotten around to a FCM yet. I just wanted it sound better, louder without being offensive. As for performance,it can already pull stumps out of the ground