86 560SL: another vacuum/trans. issue

Hey everybody,

my SL is shifting hard (upshift only) again. I have read pretty much every thread that came up with the related search results but couldn't find anything useful. In November last year the car was in the shop where they replaced a vacuum line which helped a lot, since there was close to no vacuum. They also said there are still vacuum lines to be replaced to completely resolve the issue. The car was then driven for about 100 miles and then left since I was overseas until last week. When I took the car out after removing some rat nests, I noticed it shifts up harder than it did in Nov. Maybe the rats got to some vacuum lines. My question is: Is there more than one line going to the transmission? Shouldn't there be only one running directly from the intake to the modulator? If so, wouldn't I just be able to replace the line and the modulator? Or are there any other things I could/should check?

Transmission oil and filter replaced last year with almost no miles on it, modulator has been turnend by one complete turn counterclockwise.

Thanks,
Max