I have now replaced my vacuum lines on my 86 GL two times due to them swelling and coming loose. My assumption is that it is being caused by excessive oil or oil vapor in the lines which the rubber absorbs and expands as a result.

The engine is a 1.8L TBI and the line that is swelling comes out of the manifold and then Ts off to the transmission and to something by the passenger side strut tower.

Could these lines possibly be removed? I have removed the line coming from my TBI running to the EGR and noticed a definite improvement in idle and little better start up power.

You may actually have a small leak in the transmission modualtor valve. The line that goes to the tranny is going to that valve and is required for shifting. Look inside the line off the tranny and se if there is any red oil in there. If so you should replace the modulator and the problem should go away.

Are you using the fuel & oil-resistant type of lines?

I'm using what the auto parts store designates as vacuum lines. Far as I can tell they are just black rubber. Auto parts guys told me the swelling is due to oil in my vacuum lines, which according to them should not be happening.