2001 Silverado Map sensor not available on new intake manifolds

I have a 01 Silverado with the 4.8l V8 and a 5 speed manual transmission. Ever since I got her she does a strange thing where if I shift into neutral the rpms rev to 3k+. If I leave it in gear with the clutch pedal down the rpms go up slightly and then settle down and then I can shift to neutral. She seams to be running with less than full power. I have replaced every sensor, fuel evap canister, fuel pump, etc. I bought a smoke tester and the ken Moore fitting to test the evap, can't find a leak. I bought an expensive scanner to open and close the purge valve to do the smoke test. I am also able to do a fuel tank vacuum test and she passed. I do get a random misfire code and have also confirmed with the scanner that she runs too lean. So at this point I want to put a new intake manifold on, but all the ones available do not have a map sensor. All the intakes at the wrecking yard and mine have a map sensor. So is it common to replace the intake and delete the map sensor? I have an old Diablo u7198 on revision 2 that lets me delete EGR and other things. I'm not sure if map is one of them. Anyways, just looking for opinions on getting one of these new manifolds.
Thank you for your help