Hey, 1.6 Stylance here too. Have found this quite a few times. Definately runs better with optimax/ultimate fuel, quieter and more responsive.
Ive found that, especially in cold weather the engine seems to do its own thing, with quick revving around the idle mark (turning the aircon off seems to chill this out) with a hard rev clearing it out somewhat. Ive also had it stall a few seconds after starting cus of this, so had to use the accelerator to keep it running at idle.
I find the engine doing what it wants quite often, such as when pulling away, still on the clutch at just over idle it will rev the engine as if it thinks its going to stall. And the engine braking effect seems to differ, sometimes requiring the foot brake to slow down (2nd/3rd gear 15-20mph searching for car parking spaces).
Ive also felt a strange rocking while cruising about 30-40mph in 3rd/4th and looked down to see the rev counter bouncing up and down between, say, 2500rpm and 3000rpm. No idea what this is either.
Has anyone else found this at all or is it some bad driving technique I must have? Any fixes wlecome too, as it is due for service any time now.
Jon