Fant dette. Vet ikke hvor troverdig det er men det virker som karen som har skrevet dette har peiling.....
Håper det gir deg svar....
EXHAUST
The factory exhaust manifold is very good with all types, both FWD & RWD, and up to about 200hp they are better than just about every aftermarket exhaust manifold available.
They are a 4-2-1 design, and all types fit all the engines, with the exception of the 20v manifold, which has the two bolt holes on the extreme ends in a slightly different place to the 16v ones. But - by slotting the holes on the 16v manifolds, they can be made to fit quite easily on a 20v; usually this is done to convert a 20v to a RWD car. You'd be far better off getting things such as lightweight flywheels, etc, to improve performance, as the engine will definitely benefit from these, rather than one of dubious increase at best..
url:
http://www.billzilla.org/4agstock2.htm