The earlier magnums were underpowerd. Id test the tps and i think theres a mod you can do to get better throttle responce. Im not sure if it would help your problem thought. My only other advice would be to look into some cheep bolt on's. I recently replaced my air intake with the mopar proformance intake and it deffinatly helped accelerate to and maintain highway speed even with my lift and tires.

 

I dont believe i have a EGR exhaust gas recirculator. also i dont think its the fuel pump cause it gets like 10 mpg. If the fuel pump was starving the motor wouldnt i get a CEL because of a lean mixture situation, ALso question for 1bigramaniac do you have a 360 or 318?

 

Not the problem of the 318, performance wise they are about equil.

 

Well then why would dodge put two different motors in the same truck. there has to be a dif in HP and Torque, more Cubic Inches=more power

 

Well if the engine is screaming and it isnt going anywhere, that is a transmission problem. Did you replace the TC? Either the TC is bad or the clutches in the tranny are slipping.

 

Just rebuilt tranny, 3 months ago, plus new torque converter. if thats screwed up again im gonna part it out. cause im tired of putting money in it. Should have got a cummins in the first place

 

The 360 has about 10 more hp and 30 more foot pounds of torque. I have a 318 in mine and she runs like a dream with 260,000 miles on her, lots of power and with the little bit of mods I have done to it i can launch faster than my brothers mustang and hang with it till he hits third gear.

 

but does it cruise nice down the highway??mine feels like im pushing a car in front of me

 

I HAD THE SAME PROBLEM. It turns into a dog going up hill. First, check the tranny. When was the last time you had the fluid CHANGED and the tranny filter CHANGED. That can help. Also, get the Lucas Oil Tranny additive. That helped me out Soooooo much. Also, when you change your oil next...use that motor flush stuff. Just add it to your oil before you change it and run the engine for 15 minutes. Then change your oil.

Also ask yourself, "When was the last time I changed the car/rotor/wires/plugs? OR THE O2 Sensors!!?!?!?" YOu will think your truck is brand new.

 

Yea, plenty of power on the hwy can do 110+ easily. I also think it sounds like the tranny but mine did the same when the cat, which i thought was completely gutted, had a piece that came off and partialy blocked the outlet.