1999 dodge ram 2500 5.9 360

If the plenum gasket is bad you would notice that you use a lot of oil. You may not even smoke much if this is the case. At least thats how it was for me. When you say louder what do you mean? The exhaust? Do you have any holes in the exhaust before the o2 sensor? It would definitely affect performance but i think you would notice it more when driving. Any other symptoms? Using more fuel? Shifts fine?