IMO the larger hose is always best due to less restriction. Remember, length & bends affect it. The filter alone is a restriction. BUT, I ran #6 (3/8) hose on my 235. Having installed all this at the engine build I have no 'before & after' numbers to compare. You don't say if you're running a by-pass filter also, but that also drops the PSI of course. I saw 30PSI on my S-W dash gage usually. Might be at 20 or 25 sometimes. This was running regular 100 mi. runs in temps at 115 deg. or more. One of my first trips was Yuma to Phoenix on 4th July, it was 118 to 120 that weekend. Ea. way 160 mi., came back in afternoon. Nice looking truck you you have. Hope this helps - Doug
