On the air induction tube on an LS engine one CANNOT have more than one bend. Didn't like the looks of the cone shaped filter being crammed into the front corner between radiator and inner fender as well as leaving no horn room so curved the tube back over valve cover, much prettier. We switched mass air flow sensor and accelerator pedal with those from a perfect running Olds with identical engine and the Olds still ran perfect with the switched parts while the AD still ran like crap with it's new parts. Fuel fine, electrical fine, everything checked out. Finally sunk in our thick heads the only change made was going to the "pretty" induction tube. Cut second curve off and it purrs. Never had this problem with a Rochester one barrel. First pic is a test run with a single curve tube (ran fine) and second is the pretty tube witch gave a sick running engine. We are still learning.
Before I had my '49, I had this old Jag with a 5.3L LS motor stuffed in it. I had it tuned on a chassis dyno and when I came to watch the run, the tuner had taken the intake tube (just a 90 bend to get the filter off to the side of the engine) and had it turned straight up sticking up into the air. When I asked why, he said that he was getting erratic readings from the MAF and rotating the filter up into clean air helped. Once the tune was done, the intake was rotated down to where it's shown in the pic, and the car didn't seem to suffer any drivability problems that way. My 2003 GMC with the 5.3L has a the factory airbox and tube removed with a K&N straight on to the MAF - never any problem. It must have something to do with the air moving faster on the outside radius of a tube and when it gets to the MAF if confuses it. Trying to get a straight air intake tube on my '49 with the 5.3 and side-step this issue. Had thoughts of turning the intake down with two 90s, but your post reminded me this isn't such a good idea.
That LS engine sure looks at home in the Jag. Put an old 400 small block in a 1979 XJ6L for a guy years ago and he later told me he had a complaint; with the Chevy engine he said his driveway was getting rusty due to no oil dripping on it.
