I dont' know about checking the inside. I know that there's an air cutoff flap in there, that if there isn't enough vaccum to open or close, whichever the case may be, it would cause the symptoms you are talking about....

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Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic