When I worked for a FLM dealership, I was able to use the IDS computer system to check my fuel trims. With all of the vacuum leaks, the long fuel trim was at 22/23% positive. When I removed the vacuum booster line, it went down to 12/13% positive. I still had a big leak. Now, that i've taken things apart, I found out that the drivers side imrc actuator was a major leak. My mityvac tool couldn't draw a vacuum on it at all. I've since repaired that down to a little leak, and just installed a new actuator on the right side.
The imrc plates have mini bearings, not bushings. The part number is 1680D. It is manufactured by NMB corp. Here is the p/n breakdown:
16 = outside dia. in mm
08 = bore dia. in mm
D = Single seal on each side.
While turning the drivers side, I noticed that the inner bore did not turn with the rod, I figured air was getting by the rod. I innitially thought that the rods were pressed in. When I removed the rods, I found a seal on both ends. It was hard and brittle. I used a pair of small dykes to cut them. They just broke apart. They were prolly carbon seals. I went to autozone, and purchased 4 orings, with a 9mm o/d - 5mm i/d - 4mm thickness. They were a tight fit in the bearings, and actually sliced off a little sliver of material. So now I have 4 custom fit o'rings. Hopefully that is where the leak was originating from. I'll let you know when I get it back together.