Possible Engine Upgrades

I have a 1995 454 TBI on a 33 ft Class A that weights about 15,500 lbs traveling weight. Stock it was 230 HP and 385 ft lbs of torque. When I first got it, it took 22 secs to go from 40 to 60 mph. A tune up, new wires plugs cap etc brought it down to 19 secs but it would still down shift on the slightest hill with the 4 speed transmission and ran hot enough to kill the spark plug wires. I installed Thorley headers,a FF muffler, 10.5 mm ign wires, and a CAI. 40 -60 times dropped to 14 secs a notable improvement with no down shifting on the same hills. Greatly reduced heat with the same ign wires on for 9 years. Advanced timing from 4 degrees BTC to 9 and that reduced 40 to 60 mph times down to 12 secs. So yes you will add about 75 or 80 HP and the equivalent amount of torque and is worth the $1000 that I spent. I saw no improvement in mpg with these mods except maybe .2 mpg with advancing the timing. I have averaged 8.7 mpg over 80,000 of travel. This vintage eng makes max torque at about 1800 rpms so you don't want a 4 in or greater exhaust unless you are going to race it at much higher rpms. A 3 in single or 2 in duel exhaust will work the best. Hope this helps you decide.