Timing

That was you, oops
Probably the chain then.

Could an ECU cause that also?
I really don't know for sure, but it seems it could.
Hmm

TrailBeast,

Distributor is new. See my other thread. Attempt to payback #2. Advance at higher RPM is rock steady at 34 degrees, so my guess is your first response may be correct. Loose timing chain would be more likely to allow the cam to flop around at idle as opposed to when at speed.