I have been doing the rounds with the exhaust on our subaru conversions .
So this takes me to this >What I have found is the old day do two tail pipes on V8 are out ? they run a single system more power ? vacuuming the gas I was told I seen the dyno reading for my self yep more power across the range .The other thing was the size of tube used from the heads 32mm > 38mm .so what to subaru ?

so I gess there is some other input to this subject

O this one photo is a ej 20 that is going to have a super charger on the motor .I have started to make the pipe work now it is all 316 stainless steel ( food grade ) 50mm

Not quite sure what you mean there...
From a motorcycle point of view, I know from experience that a 4-2-1 exhaust produces a better spread of power and lower down torque, where as the 4-1 exhaust had better top end power.
Regards Subaru EJ20 n/a, I read an article on the iSR Performance web site here http://www.isrperformance.com/technical.html  that you should not go any larger than 2 1/2" exhaust.
The other thing I read is that there should be a step between the port on the motor and the header - something to do with back pressure? .. can't seem to find the reference to that at the moment though so I don't know if that was for n/a or turbo.

Yes it stops the gas going the wrong way as well ,I show you when i finish it soon .seagull

[Edited on 6-8-2004 by seagull]

[Edited on 6-8-2004 by seagull]

Here's a pic of the MRT set-up for non-turbo. You can see what I mean about the 4-2-1 setup