hi mate if this is a 1.3 c.f.i the single point fuel injection it could be 1 of about 3 i could think
1 if its lacking power as well there is a map sensor hose that often claps this runs from rear of bulk head to valve on manifelt and will be all soft not allowinf vacuum from map sensor
2 it could be a faulty throttle position sensor these can be checked quite easily using a multi meter or just by visually seeing if there is any wiring damage,
3. its always worth cleaning and greasing the main connections to throttle position sensor, idle air valve, vehicle speed sensor, and mainly module,
if it is the efi model i have known inlet manifolds leaking which could cause a number of faults
hope this helps,
paul, January 2007