So I have noticed with my truck on acceleration, the gas pedal is only responsive from 0% to about 50-60%. Pressing it to the floor doesn't increase acceleration it just kinda flatlines after that... I feel like it's just making the truck run richer without providing additional acceleration. I will add, this is a manual transmission. I'm thinking it might be the throttle position sensor but wondering if anyone else has experienced this?

 

Check the throttle cable.

 

I would start as already said, check throttle cable, is it opening the throttle body all the way?
I would then put a fuel pressure guage on and see if it is loosing pressure.

 

How exactly would I check the throttle cable to make sure it's opening the throttle body all the way?

 

If you don't have a helper who can hold the gas pedal to the floor, wedge a board against it to hold it down. Pull the air hat off and look down the throttle body, the throttle plates should be wide open (vertical).

Judging from your description though, I don't think that is going to be the problem. Does it feel like it bogs under acceleration? Any misfiring, or engine light coming on?

 

I don't think it's misfiring; no engine lights come on. If I am doing WOT and shift and get back on the gas immediately, it's like I lost a good amount of power and it lags but if I take my time between shifts it's more linear in acceleration. It lurches a lot when taking off and between shifts so I'm thinking tranny and engine mounts?

 

If I'm reading your description right, I'd call that bogging - like it doesn't want to take the gas too quickly or it will "bog".

You could have a fuel filter that's clogging, or possibly a fuel pump that's going out. Another thing comes to mind too, and that's your catalytic convertor. I believe that is a symptom of a cat that's clogged.

 

I agree with ragged89.
Let me say, I have never worked on a magnum motor, but assuming its the same as chevy or ford, there should be a pressure tap on the fuel rail. You can hook a pressure guage to that, tape it to the windshield, and drive the truck. Pressure should hold steady, and possibably raise a couple lbs on full throttle. If the pressure drops, you have either a restriction (usually a fuel filter) or a pump that is going bad.

One other thought. With the motor turned off, remove the air cleaner hat? open the throttle and see if you see oil pooled inside the intake. If so, you probably have a bad plenum seal. (lots of post on this) This would need to be repaired and its possible that with enough oil being burned you have plugged the cat.
But if it was mine, before I replaced the cat, I would seperate the exhaust and see if it runs better.

 

@ ragged89, I checked the throttle plates and they are vertical. @ 93 ragtop, I looked inside the intake I don't notice any oil pooling but there is a coating of oil and black flecks, carbon? inside the intake and there is the same thing on the inside parts of the throttle plates. I don't really have a muffler, the old one rusted off so my "exhaust" exit is around where the cab and the bed come together.