1999 dodge ram 2500 5.9 360

today in my 99 ram 2500 4x4 5.9 magnum with no real warning just kind of went into limp mode and wouldn't accelerate.
Over the last couple months the truck has been acting strange but only for the most part when at a low idle or low vacuum,like shifting the trans into rev after the truck has been running. And alot of time the turck would die i thought it was the IAC mod but that didn't cure the problem. This truck only has 78,000 miles so i thought maybe it was time for a tune up i did replace the plugs a couple weeks ago but didnt change out the cap and rotor or the wires.
The truck did run better but for some reason the truck got louder and I thought it was because I knocked the exhaust loose hauling wood but today the truck is loud and a dog and i cant figure out why. I went thru everthing and it appears to be in order. I checked the exhaust and its tight. I have heard of problems with the intake gaskets going bad and the truck running and burns oil bad is this some signs of the issues im having
Thanks Aaron