If i bulid a custom intake for my 91 using a BHAF what size tubing do you suggest for the best balance between too little and too much?

 

I used a piece of 5" aluminum irrigation pipe and the elbows off my old tubing

 

A normal paper BHAF should have a 4" inlet and so does an intercooled cummins turbo. Might as well just use 4".

 

I built one and used 4 in. pipe with 2 45 degree bends and a big K&N filter. It looks good but i am going to put a shield/box in sometime. it helped with out box about 1-1 1/2 mpg alone. then i painted it black with plastic spray paint. Long enough to sit down to collect fresh air through head lights.

P.S. Very hard with what pipe i used to get on filter, but with perseverance its on and clamped good and tight!!

 

amen to the getting the pipe on. The 5" was a b 'otch. Onlt reason I used 5" was because there was a pile of irrigation pipe lying near by. It toke two people and a heat gun to stretch the elbows over the pipe. free is always good.