Now using Guru on WSM-How does that change things?

Hoz yea you need to seal the other intakes and let the Guru do it's thing. If i use the ATC i'll usually just let the smoker get up to temp naturally with the vents open then turn on the controller to keep the temp....some do let the controller bring it up to temp but imo vents open is better than air blasting on the coals.

A couple things to say about this, a lot of people will just use vents to bring it up to temperature. Either way works. But when using the Guru you need to have all other intakes sealed. Otherwise the forced air will find the easiest exit, which will not be past the coals and up to the top vents, it will instead simply flow out the other open intakes.

One thing to note is the position on the fan damper. Assuming you have the 10 cfm fan the damper should be about half open I would say. Your damper may be choked down too much making it heat up slower than normal.