i have a miltek system, had it for 3 years or so. the system has seen 3 different setups...
- miltek with cat in place. (nice sound but too quiet)
- miltek with decat (louder, crisp and raspy sound but boomy as hell on motorways)
- miltek with cat in place (2.5" exit) and centre section removed. (best all rounder imo. crisp, raspy and not very boomy)
i decided to remove the centre section because it had collapsed and the joints are always seem to be blowing. so i have done away with the cat exit joint and the v shape joint, doesn't blow at all now and sounds great. not much different from in the car than a miltek with a cat in place only very slightly louder. i will never go back to a decat, the boomyness made me feel sick on long journeys.
plus there is no horrible eggy smell with the centre section removed like there is a decat and there is no swapping things over for mot, and you dont have to lie to the insurance company and risk your policy. no brainer imo.