i dont know if i am in the right place.

i have a 1600cc 1998 megane.
my problem is the engine sounds very lumpy as though is only running on 3 cylinders,but its not,have changed all the injectors and plugs checked the compression.
when i start mornings it ticks over at aboput 1100 revs,after i have been driving for ten minutes or so everytime i come to traffic lights or stop signs it ticks over between 1500 and 2200 revs,
anybody have any idea's
thanks in advance
dave