the screw should be adjusted out, ie CCW for more boost. You can place a shim under the ALDA to see if it will increase acceleration (it should unless gunk is blocking the boost line to the ALDA or some other maladay) then go about removing the metal cover (I peel them off using sharp diagonal cutters) to get to the lock nut. IN fact I just put a copper washer from an oil filter set under an ALDA and decided it ran so great I just left it that way. The shim was too thick for a fine tuning. A purist will want to remove that cover and live with the ugly results. maybe I should get out the dremel tool next time and try doing a neater job, tearing it off leaves a bit of a jagged metal around the base of the cover.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!