Engine stumbling at certain rpm
 

Hi guys, This is the second time on this topic I guess cause I'm still a little foogy . I have been having the engine stumble a little bit between 2250 and 2500 rpm on my 96E300D. I cleaned the one butterfly valve in the air passage way and I think Doc said there was a second. Is it in the right hand or drivers side of the air intake tube? And if so I see that there is some sort of lnkage tied to the underside whats the procedure for taking that apart?The car pulls strong through that part of the rpm band and will sit above it all day with no hesitation but it just so happens that is right around the speed limit. Thanks for any help I get
Burgenlander

96E300d
380SEL
380SL
240D