I know Benzmac will shoot me for this, but here goes:
The adjustment on the plate he talks about is (on my M103 engine anyway) blanked off with a welded metal plug.... What I did was to remove the bar across the top of the plate (with 2 hex screws). Remove the rubber 'bump stop'... then contruct a new metal bumpstop with a screw thread. Place a bolt in this, so I can adjust the rest position of the plate up and down as I see fit. (change in season).
Works for me anyway... car now starts perfectly (unless its been sitting for days).
Dont try this if your DIY skills are poor... a screw falling down into the air intake will 'screw' your engine.