Well this is just my personal opinion. I wouldn't bother with the manifold unless you're planning on more tuning (reduction pulley, CAI etc). Sounds like a waste of money to me. Consider a one-ball conversion, it's cheap and gives a little extra noise.
I have an S running the miltek rear section and a miltek manifold. Its very loud with both once the foot is down and your above 3k rpm! Inside the roar from the manifold is quite intrusive at full throttle acceleration...not too bad though when cruising or being gentle (Its all personal preference) The manifold give the stock exhausts and JCWs a throatier sound but the miltek back section is what really makes it sound sporty.
I'd suggest the cat back as first buy and a mani later. Either item will make the poppling on overrun more noticable but the cat back section will make exterior acceleration noise more sporty than the mani on stock exhaust.
I imagined free flowing cats would allow the engine to breathe better , have you tried the manifold?
Did you notice any changes apart from noise, e.g torque or fuel consumption?
It sounds like you fitted the manifold first , did you consider the one-ball solution before you bought the rear section?
WIth the pair fitted do you have any problems with the neighbours or police?
I fitted both at same time but I have driven a S with just the cat back section.
I have never had an issue with the neighbours (but I live in the middle of nowhere) even when I'm down in my other halfs town where she lives in a residential area. The police have had a look at me as I have gone past in the other direction in town at full throttle away from some lights but TBH the milltek can be quiet if you drive gentle. It is very larey at full throttle but quite gentle and burbely at low revs. If you pull away and throttle up to 4k -5k rpm before changing then its loud with a capital L! If you change at about 2k rpm then its quite and all you get is the poppling and a nice throaty purr.
The manifold does make a differewnce to the car. It was far torquier and there was even a slight improvement in the feel of acceleration. It was better than just having the exhaust IMO after driving someone elses with just the exhaust. However the warning is in the loud with a capital L....with the manifold it is very loud inside the cabin under full power throttle .... but I love that. Drone is a bit worse with the manifold but if atr 70 on motorway its OK and the radio can drown it out without too much trouble and conversations are not difficult.
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