Vacuum headlight question

[J-440]

 Been chasing a headlight door bug for awhile now.  Everything is new from the dash switch to the headlight pods.  When the engine is running, there is so much vacuum (17psi) that my switch will not move at all.  When I pinch the small hose that goes to the canister, the switch will work and the lights come on but the doors will not open.  When I let go of the hose, the doors open.  This also works the same turning the lights off.  I've tried the small plastic hose reducers in the line to the canister but I get the same results.  This is not a stock motor so I'm assuming I'm pulling more vacuum than a factory 440. 
  Would a vacuum reducer valve work from a parts store or am I missing something?  Thanks.

[68 RT]

I have 18 inches @ idle and don't have any problems. Sounds like a vacuum line is hooked up wrong or you have a bad switch. 

[cdr]

try lubricating the vacuum part of the switch, the rubber seals are binding under vac.

[J-440]

Great, the joys of working behind the dash. Thanks for the help guys.