Join Date: Feb 2013
Location: Aussie in Sweden
Whilst by no way being an expert on exhausts it sounds like you just need a mid section and tail/rear section. If you want something that isn't too loud I would get both a silenced mid and rear section.
I have no idea about your MOT procedures so can't comment on the emissions but a straight through exhaust means that the flow is unobstructed through the silencer as the silencer has no flow reversal. Basically this means that typically the gasses go into a series of chambers and depending on the shape of the chambers, the gasses can move around in helical or other patterns back/forwards through the silencer to increase pressure. However in a straight-through silencer the gasses do not pass back/forwards through these chambers but rather simply run 'straight through' which results in a lower pressure build-up and typically, at least from my understanding, means with a straight through you will get less back pressure (so less power) and they tend to be louder when compared with chamber silencers and will have slightly higher emissions (as the gasses are passing through less material).
At least that is my understanding from the research I have done. Could be totally wrong so would wait for someone else to chime in but that is my understanding on the straight-through question. So it would seem to be like you would want a chambered silencer and not a straight-through as you want better control of the noise.
2000 Alfa 156 Sportwagon 2.0 TS CF3
2002 Alfa GTV 2.0 TS CF3
1983 Porsche 944