1998 Mustang GT Missing at 2500 RPM

Hey guys...I got in my car today to go to lunch and it started running funny. It seems to be missing at 2500 rpm and feels like it is being chocked. During idle it sounds like it has a small hick-up. When I get on the gas in any gear it just feels like it is chocking. I have an O/R H-pipe with Flowmasters. It ran great until this afternoon. I checked the plugs and it looks like they are very new, clean with no black on them. I have had the car for a few months.