Hpi Misfireing?

[Guest spritemajor]

Hi all car is 51 plate HPI been running great for for 14 months then got Anti-polution fault and had EGR valve replaced acceleration is better than ever and through the gears but on low speeds 2000rpm -3000rpm it juders missfires ? like on older cars when the condenser was on the way out starts first time mileage 88,000 i know plugs were changed at 40,000 i bought it at 76,000 dealer said they serviced it so they may or may not have changed them if a change of plugs dont cure it could it be the coil pack? any ideas would be great Regards Mark