So, my brother has a 2003 Mitsubishi Eclipse GS and he has a couple of issues with the car. The first one being that it will occasionally if he comes to a stop, the car completely stalls and dies. The second issue with the car is that if you press the pedal to the floor, the rpms just bounce between 1500 and 3000 rpm. The only thing we could find that the previous owner did to the car was putting an ebay air intake and an aftermarket muffler, but everything else looks stock. I did replace the coil packs and the spark plugs on the car, but that didnt help it.

Does anyone have any idea what could cause those problems?