I just bought a 2nd FD and while I was poking around I noticed a "mod" on a sequential vacuum line. Looks like a line was removed from wherever it went and a filter was placed on the line. Anyone know what is going on here or what this does?

click for big

 

a vent filter on manual tranny car on the double throttle control solenoid

 

so was that line supposed to plug into the open nipple?

 

No. The open nipple should be open. The filter is in the right place, so no worries.

 

The backside of the Double Throttle solenoid isn't used unless the car is an automatic:

http://www.fd3s.net/vacuum_hose_diagram.jpg

On a manual, its just vented.