What are the most commen signs to tell is you have a bad plenum gasket???? just recently I've lost a bit of gas milage, also notice a rough idle when at stops and what seems like a dead spot in the peddle when pulling out or under load-----gots a brand new cat and head pipe, and exhust all the way out the back, new o2 sensor and complete new tune up filters etc etc,,,, and none of that has helped the dead spot or rough idle...could it possible be the plenum gasket?

 

from the dodge ram faq therd at the top of the 2nd gen fourm

Blown Plenum:
Look down into the intake manifold and look for oil pooling on the bottom of the intake, get a mirror and flashlight and look at all of the corners. any oil means your plenum is leaking and it needs to be fixed (APSPrecision.com for the kit). Get a new TB gasket when you put it back on and torque it down to spec