What is the purpose for the sleeves and can they be removed? Would there be any reason to remove them? Would the exhaust flow better without them?

 

Those sleeves get Very hot to burn off extra exhaust gases. A emissions thing. They can be removed, although I've read to be a diffacult thing. They don't really restrict much. Removing them won't benifit enough for the work requird. (Please forgive my spelling) If you really don't want them I sugest a P90 or N47 head. As they don't have them.(correct me if I'm wrong) all in all. Leave em be. There fine.

 

x2 on that.

 

the n47 has them. you need a e88, or n42, or e31 then they are gone. but then its square port exhaust, and a different header. manifold stays the same

 

I've wanted a E88. I heard they flow pretty well. And the large valves.

 

Thanks for the info. I'll leave well enough alone.