MSD recurve

I changed the springs and bushing in my MSD distributer this week end. I took out the two heavy springs and put in one light and one medium. Also swapped out the stock bushingg for the blue 21 degree. The total is now coming in at about 2700rpm....Pontiac engine here also. I like this set up much better, as it rev's faster.
However, when I set my inital timing at 13 degree's, the engine was idleing, but shaking, I increased it to 15 degree's the engine speeds up, smoothed out, also giving me the highest vacume. I have alway's heard, set the initial to the highest vaccum, then retard it two degree's, for WOT. But the lower timing gives me a rough idle.
Am I wrong here, set it at the smoothest idle or retard it for the higher RPM's? 10.5 compression, plenty of fuel, and even at the rough idle, I still had 12" of vaccume.

Basically, is there a rule of thumb here?

Just set the advance at idle where you want it. As long as it doesn't effect off idle performance it shouldn't matter. I'd go with the advance setting at idle that gives the best off idle performance, then set the rest of the timing curve to carry the mid and top end of the RPM.

Funny how 1 degree can make the difference.....:rolleyes:

Engine is 400, .30 over, stroker. 461 now.
Heades flow at 310 cfm, dual 600 holley carbs, Offey 360 intake, Msd digital 6 box.

It idles perfect now, and I am pulling almost 17 " of vaccume now.
I will try wide open tomarrow, I will see.

Thanks...