[JLMounce]

Timing was recently checked late last year after I replaced the harmonic balancer. It's computer controlled with a locked out distributor. It uses an adjustable rotor that was also locked down and additionally loctite added. But it doesn't hurt to check those items again.

Besides removing the heads, is it possible to determine if a valve seat is moving?

I have not had to re-adjust my idle. However it's important to note that the system uses an IAC valve, so changes in idle are compensated for by opening or closing that valve as needed. This may hide any timing abnormalities that you may notice with a carburetor. I have not noticed a change in IAC count behavior, but admittedly it's also not something I track closely.