I considered doing the ashtray setup (very nice work Jeremy) but I had just swapped in the 92 ash tray from the 190e and its got a much nicer action than the 87 plus its handy for storing quarters. Instead I drilled a 1.5" hole in the switch panel where it had 2 blank spots and installed a 15psi fuel pressure gauge ($8 ebay) to act as a boost gauge. Works beautifully. The only down side is that it tends to vibrate and make a buzzing sound. The solution was to add a cheap fuel filter in line with the hose which dampens the vibrations for the most part. I still get a slight buzz from the gauge at 12psi which is handy at night since the gauge is not lit.
http://i.imgur.com/aqZkg.jpg