For improved power, we're dealing with the basics here.
> Fuel delivery
> Air flow in
> Exhaust flow out
> Ignition timing
Fuel delivery - I assume your 454 is fuel injected so a fuel pressure check, preferrably under load, will tell you if the pump and regulator are performing properly. A fresh fuel filter should be installed first.
Air flow in - Fresh air filter. Check for kinks or restrictions in the air inlet tube. Note that critters seem to like nesting in these areas.
Exhaust flow out - Factory manifolds and exhaust are fairly restrictive and designed to be quiet and cheap to mass produce. Headers and a large, free- flowing exhaust system will free up many needed ponies and reduce engine temperatures. Coated headers are recommended.
Ignition timing - I'm not sure if the '94 454s had completely computer controlled distributors. If yours still has internal timing advance weights, they could be sticking. Motorhomes tend to sit a lot and a common problem is frozen advance weights - absolutely kills performance. Also, I remember seeing a thread on a different RV forum about a custom computer chip with revised timing curves that work well for motorhomes. Made a lot of sense, but I have NO personal experience with this. Here is the link to the last page (of 11) with the pertinent info. Worth reading all 11 pages!
RV.Net Open Roads Forum: Tech Issues: Timing Curve - 454 TBI - 1991
Best of luck and Happy RVing!