Trying to adjust choke

I understand that it doesn't have a carb, but the plunger that acts as a choke is run on I am guessing vacuum. I am needing to figure out how to raise the it a couple millimeters. I am not mechanically inclined, but thanks for the responses anyways.

When I manually adjust it while the car is running with my hand it idles smoother and doesn't sputter out.

is there any way to adjust the plenum? My altitude changed 870 meters when I recently moved this month. which is why I am being told its my air/fuel mixture.

I had the car in a merc shop a few months ago to replace a bunch of wiring, because of AirCare standards the mechanic played with the fuel mixture to see if he could get it to run cleaner, which it didn't and sat in my carport. After a couple months I bought a house up north and here there is no AirCare standards and I was able to put it back on the road where it died in my driveway one day and the mechanic had to come to my house where he said he made the fuel mixture too lean and it wasn't getting enough gas. It could be that he changed it too far the other way and the difference in altitude.

Unfortunately he is on the coast and I now live 5.5hrs North of him, he had all the tools needed. I heard there was a local merc mechanic in 100 Mile House, but I haven't checked him out yet.