My car threatens to die during idling...the rpm drops down low and then goes back to normal. It started doing this during driving too. I just had the fuel filter and a few other fuel related things replaced. Any idea of what it could be?

Here are the most common causes of surges, stalls at stops, low erratic idle speed, rough idle and engine hesitation, it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.