[PxTx]

Tony, you can place a temp vac gauge to verify this but the highest vac will always be with your foot out of the throttle. Light cruise with a slight load should not allow the vac advance to add enough timing to detonate with a proper tune.

My dad has always made a point with theze timing 101 articles to note that the vac advance needs to be limited to no more than 10 degrees due to the typical pump gas we have. I'm on my phone and don't want to go into details. Though engine tunes and config vary- they all act surpisingly similar in off throttle conditions (highest vac)..