86scotty
Cynic
Couple of things I want to point out. When you see references to newer V10 and the 5-speed automatics, those are the newer 3-valve engines. Without actually looking it up I think they have an extra 80HP or so over the older version you have. I remember an old neighbor who had a V10 motorhome and traded it in on a newer (and a little bigger) one. Went from the old 2-valve to the new 3-valve and was really impressed at the improved performance.
The general rule of thumb is adding 4WD eats 2MPG. Loose another 1MPG per inch of lift. Not always true, but generally pretty close.
I'm confused here too. I wasn't aware that any E-series, even chassis cabs for motorhomes, got the 3 valve. I had a 3 valve Expedition 5.4 and it was absolute garbage. Nothing but trouble. I'm not hating on 3-valve v-10's but that experience was bad enough for me to stay away from 3-valve Triton motors forever.
My 05 MH is a 5-speed (5r110) equipped 2 valve v10. I added an AFE intake per CarringB's excellent advice and a 5-star tune after tuning 3 or 4 Fords with 5-Star now. The performance is amazing. It's a 25' MH weighing 10,700 loaded and drives like a car. I can only imagine what it would be like in my 98 V10 van but don't have the funds yet.
Another note, don't tune a vehicle expecting better fuel mileage. That's a pipe dream. It will perform a lot better but you won't see an MPG improvement. At least not in the few I've done or anything I've ever read (other than advertising). It's still well worth it.