Ok I found that with the A/C on and the EC button depressed while driving...the air starts to blow out of the center vent more regular. With the EC button off the center vent will blow without the accelerator pedal depressed and will stop when you accelerate with the loss of engine vacuum!! I think I understand what you are saying but it seems to do the opposite because when you depress the EC button the vent starts to blow more regular and is not that dependent on engine vacuum!! Did I do the test correctly?

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DRIVE HARD-DRIVE FAST-DRIVE TO GET THE HELL OUT OF MY WAY.

1986 190E 2.3-16 Pearl Black!!
1987 190E 2.3-16 Smoke Silver!!
1986 190E 2.5-16 Pearl Black!!
2004 CLK 500 Cabrio Designo package!!
1994 E320 Cabrio Red with black top!!
1985 500 SEL Anthracite Grey !!
2011 Subaru Impreza STI 380HP (Yeah Baby)