EGR valve
 

I have an '86 560SEL 3.8 and have been writing in about the exhaust smell in the cabin. One reader in the search area wrote it might be my EGR valve, which I checked and it did not have the appearance symptoms he suggested, but supposing it is- would any of the follwing be syptoms as well :

Poor accelaration perfomance after warm up ;

Excessive smoke( blue ) from the exhaust pipe when accelarating away from a stoplight BUT only occasionally ,not every time ?

I've sealed off every outside vent I can find and the smell is still filling the cabin at idle.

Any thots ????????

Thanks