off the top o my head....that CAC.com write up on the secondary vac system has the conditions for 2* engagement. I'd go back over that list of stuff. % of throttle, closed loop, oil temp, reference vacuum signal (MAP under the ECM). I know I'm forgetting something here, sorry!
How smoothly do the 2* actuators work? I know that some don't work smoothly at all due to mfg'ing defects upon assembly. I remember reading that over at the NetReg site in the maintenance section....I think Gordon had a bit to say about that issue. The arms were not squarely in the center of the diaphrams and when they pull the throttle levers they don't work smoothly. Also Grodon said that to make sure that when installed test them with a hand pump to verify smooth operation. I know I had to play around with mine....swap from side to side and flip them in order to get both opening smoothly and the same amount at any given vacuum setting.
Jez, does any of this make sense to you???
Tom