Recently i found that i may possibly need new engine/tranny mounts, havent installed them yet and do not know if this is related, but for the past few days while the car is sitting idling, it will sometime randomly drop 300-400 RPMs then go back to idle RPM a secod later. Is this normal? No check engine light has come on.

Another concern is im hear a rattling noise coming from the car, this sounds almost like pebbles being shaken inside of a tin can. It is most prominent when im in 1st, 2nd, and sometimes 3rd gear, within what i believe is the 2100-2800 RPM range, coasting (and decelerating without foot on clutch), and when im on a incline (havent really heard it when on flat roads). And generally foot is off accelerator too. Not sure if this is bad or not, no gears popping out of place, no or very little engine shudder (that i can feel at least).