JTT - good luck to your mate 'knocking out' the pre-cats.
One might be do-able but the other is quite inaccessible - too far up/down bendy pipes to get to.
Doubt you can do the job properly without cutting them open - unless they're already knackered.
Morph - until someone mentioned it and i looked under the covers myself,
i hadn't realised how puny the pipework is off the head .... must be restrictive.
I gather (from Mat + Mark) that temps in there can be 900deg or so which isn't good ...
except for warming the pre-cats to operating temp quickly.
Manifold / header design can be very complex ...
Factors such as scavengeing (using gases from one exhaust pulse to help suck out those from the next),
valve overlap, tube diameter and merge points etc all play a part.
I think i'm right in saying it's more critical on naturally aspirated motors than turbo'd ...
the latter you generally want to get gases away asap.
Supercharged i'm not so sure - in theory i can see fors and againsts in both approaches.
Mark - how about a swingometer for supercharged manifold / header design ...
swing towards NA or Turbo'd ? On balance, i'd guess the NA approach.
Oh and I hope these new pipes have fixing points for the stock covers ...
Let's keep things looking neat and tidy under there :smilegrin: