Slight shudder at 40km/h when accelerating

[MerrillN]

In the interests of stopping this beauty from smoking at every intersection, I finally have no lights on the cluster after a huge PCV job replacing the oil separators (yes I did the valve cover and high pressure fuel gaskets and new plugs). However, I now have a very slight shudder right around 40km/h that wasn’t there before I started the job. It doesn’t happen when the engine is cold, only after it warms up to temp and it’s not throwing any codes. Other than that one “sweet” spot, it accelerates normally. Thoughts?

Ps. The smoking issue is now 90% gone it only puffs a small amount of smoke now very occasionally. Probably valve stem seals but I just don’t have the energy left to drop the engine and do that job - it’ll have to wait for Spring. In the interim I’ll treat the oil with Liqui Moly Motor Oil Saver to try and rejuvenate the seals a bit.