I have an 04 rx8 that here in the last couple of days when I come up to a red light my rpm's drop real low and the car dies. It seems like it is hard to start after that happens. Any ideas what it could be. Alternator, coils. Could the catalatic converter do this.

 

Possible causes are low compression, vacuum leak, dirty throttlebody, carbon accumulation, partially restricted converter, coils ( should be replaced every 30k miles along with plugs and wires) regular gas instead of premium. Among other possibilities.