Centered the y-valve control horn perpendicular to the valve body with both butterflies half-way open. Moved the cable back in the bracket. Was able to find a setting in which the ram air butterfly is centered in the ram air position and the filtered air butterfly is centered in the filtered air position. However, in each case the other butterfly is slightly open. This really shouldn't cause a serious issue. The only way to fix this is with a longer reach on the control cable, but these cable controls seem to have a fixed stroke length. Alternatively, could source a shorter control horn. Set best valve travel and torqued all nuts. Torqued clamps holding FM-200 and filter hose.

Installed snubber fitting (McMaster Carr, Part # 3820K42) on #3 cylinder and ran engine. The MAP responded within just a few seconds and appears very stable.

Re-installed cowlings.