I have a 300 cells metal cat which works like a ceramic one regarding the efficacy but with a better flow. I never have smell in the car. To your question the longer the pipes the more are the lower revs enhanced you can read in the net. My manifold maker says the opposite, I don‘t know who is right. My manifold works good in the middle rev band.
On the other hand, I have a 4-1 manifold which is more suited to push the upper revs. Your both versions are 4-2-1 obviously amplifies the lower an mid section...al that is readed stuff and I cannot proof it.
I also have read a lot of contradictions in the net. I am not sure what is for which intention the best way. Better you dig in the net yourself.
Last edited by Heinz; 04/06/19 07:54 PM.
