Struggling a bit with the idle still. It seems ok during warm up but seems to stumble/ miss a beat when warmed up. Got timing spot on & have experimented with jetting but no better. Valve clearances spot on. New rebuild type 4 done about 400mls since rebuild. Got idle at 950rpm factory spec. Stumbling more when sat in drive (auto) as under a bit of load. I know folk say don’t worry just drive it but it’s irritating in traffic & I keep shifing into N to avoid feeling the stumble. Thoughts?