well my experience was with ym exhaust build, they firstly put a universal back box, no problems, then had full system built, inc. decat, first of all i had problems due to THEM breaking the lambda sensor, then once they decided it must be the decat and put my cat back on, along with a new lambda sensor, the exhaust was blowing slighty from the down pipe, no problem i though take it back and they'll fix it, they tried to but made it FAR worse, i actually ended up with zero emisions coming out the back as it was blowing straight out of down pipe! Also, where the exhuast goes over the rear bar, instead of fabricating a piece of stainless steel to go over it, they have left the original piece of mild steel in place! Eventually after almost ten visits its fixed, but i'm left with a decat thats not fitted, and the money i spent there I could have had a hayward and scott, or a prospeed exhaust built, which would have been far better quality.