I am towing a 8000lb fifth wheel. I don't know if anyone here is familiar with hwy 64 from Lexington to Asheboro, NC, but it is fairly hilly. Not mountanus or anything, but hilly. I can't hold 55 mph up the steeper hills. Even on flatter roads my truck struggles to hold 55.

I was wondering if this is typical or am I having some problem that I need to have checked. I have no warning lights or codes. I am pulling an average of 6lbs boost.

Which brings me to another question. If without the camper I am accelerating or going up a modest hill and am pulling my average 6lb boost, I'm not getting any additional help when towing correct since I'm already using my boost without towing? It seems as though I have no power or torque, especially when I have to drop into 3rd gear.

My '96 motor was replace, with a 2000 motor by the factory (prior to my ownership). I don't know if something is not set right or what, but need more power/torque.

I have just ordered Heaths PCM, PMD, and turbo master. Hope this helps, since my wife is in love with a bigger camper (100000lbs)

Well, what you've just ordered will considerably wake up your truck. The new computer and turbo master will work best with your truck's timing adjusted.

Also, look at getting an intercooler. This will keep your intake air cooler and more dense, which means you can utilize more fuel to create more power. Expect a slight increase in fuel economy as well ( ~5 %).

From your sig, it appears that you may still have the OEM down pipe attached to a 4" exhaust. Might be worth dumping the OEM, coke-can like down pipe, and going with a 3" mandrel bent unit. The difference IS noticable.

If you are still running the OEM down pipe, You really should do like wi65td said and replace it with the mandrel bent 3". Once you look at the OEM next to the mandrel bent one you'll wounder how the motor was ever able to breathe.

Not running OEM down pipe. It has been replaced. I did my last towing trip and did notice more power on the low end, but no better on the high end.

Just how much money do you want to spend? Do you do work yourself and how much can you fabricate.

You have covered all the relatively easy bolt on stuff. Next is an Intercooler!, propane, water/methanol injection and/or rebuild.

That much weight strains the 6.5 and it gets hot. Even with better breathing (exhaust and intake) you are probably seeing hot intake air temps and the engine is not as effecient. A fabbed up cold air intake might help a little.

Make sure your ac, radiator, and oil cooler are as clean as possible and bug free. Take the grill off and really really clean it with ac coil foaming cleaner get between the ac and radiator too. Most recommend the 97 high output water pump, double thermostat upgrade for reliability. With the add on you have and plan to do keep a close eye on guages especially on hills and don't cook the motor.

Depends on your economics and how much you like the truck. Might consider another truck (if you go to the 10,000 lb trailer). Any of the newer generation trucks are stronger than the 6.5 unmodified.