General:

The MSD 6 BTM (boost timing master) is a high performance multiple spark ignition amplifier that allows the the driver to retard the ignition timing based on the amount of boost being produced by the turbocharger. An engine produces the most power right on the edge of detonation, so the closer to the edge you can keep it, the better. The timing is adjusted from a dash mounted knob and can be retarded 1 - 3° per pound of boost with a maximum of 15°. I run between 0.5 and 0.75° per pound of boost. There is also a built-in adjustable 'soft-touch' rev control to protect the engine from over-rev damage.

Stock Timing Retard Disable:

The stock 'retard under boost' is performed by the dual action diaphragm on the distributor.  I believe that the stock retard is about 5 degrees or so and tops out at relatively low boost levels.  On a modified, high boost motor (10+ psi), the stock timing retard can't make the most of the situation.  Because I did not want the stock diaphragm actuated timing retard and the MSD retard to wrestle for control or overlap, I disabled the retard portion of the diaphragm.  Because the diaphragm is also needed for vacuum advance, I needed to only disable the retard side.  I removed the diaphragm from the distributor and epoxied a piece of aluminum to a pin on the backside that would keep the actuation arm from moving under pressure but would be free to move under vacuum.
 

Because the MSD ignition module is pretty good sized, I had to move some stuff around to mount it within reasonable distance to the stock ignition module and the coil (MSD Blaster 2).  I moved the stock ignition module to the battery box and mounted the MSD onto the stock bracket with a piece of thick aluminum sheet stock.  My battery box is a plastic marine type that has been cut down to about 3/4 height of the battery and is pushed forward toward the headlights to give more room for the MSD.  Wiring of the MSD is a simple follow-the-included-insturctions operation.  For the pressure transducer inside the MSD, I tapped into the line that goes into the cabin for the overboost switch and turbo gauge.
 

The retard control that comes with the MSD is sort of goofy looking.  It is a simple adhesive backed plastic box with a big red knob.  I felt it would look a little out of place mounted on my dash and that the whole thing would look better if I could mount it in a 'stock' location.  I removed one of the blank plates from my console and had a machinist buddy mill in the lettering to duplicate the original lettering.  I also replaced the large knob with a smaller instrument style knob when I transferred the potentiometer from the MSD retard control.
 

Rewiring the Fuel Pump Relay:
 
I plan on replacing the transistorized relay with a standrd relay and wiring in an inertial kill switch for safety.