I had a 1989 Falcon class b 350 with a 460 ci engine and I think a 456 ratio differential. The engine was fuel injected, ran regular gas and had a three speed automatic. My performance climbing up hills was a bit better than op's of course but would slow down significantly going up hills especially at higher elevations. I don't think op's rv performance is out of line. It is what it is and without spending a bunch of $$$ and incurring skinned knuckles along with having to use higher octane gas, I'd leave it alone. My friend used to tell me "you can't make a silk purse out of a sow's ear".
