Another transmission question

[didntdoit]

I have an 83 300 turbo, under normal driving conditions it tends to shift thru all the gears rather quickly. The first shift comes along around 10-15 mph and the other two are almost immediately after.Yesterday I was checking under the hood and found a vaccum line off at a Y connection near the brake booster. I didn't really take the time to trace it and see where it went,the general direction was towards the rear of the engine and toward the trans tunnel. I read something on here a while back about some people having similar issues. I need to check the rest of the line and replace/repair as needed.The shifting improved after connecting the loose line,if I find no other sources of vaccum loss, is the vaccum modulator adjustable? I am assuming it has a modulator as I have not had time to get under it yet,I know that some modulators had a screw in the hole that could be adjusted to change the shift points.