Rough idle on mx5

[vrooom]

I got mk1 euno roadster, the car shakes randomly, but the rpm on rev counter stay still at 850-900rpm. no loss of power all way to redline., doesnt shudder at low rev

Any idea what the cause, and how can i go on about fixing it?

Jay

[Quick silver]

HT leads are a popular replacement on the car.......my Mk1 1.6 ones were replaced with magnecor.