Help! Need rpm activated switch w/ hysteresis!!

[Jason]

I need some help here, and soon. I have a variable geometry manifold
(Schrick VGi) that uses vacuum to open up an interior flap that changes
the runner geometry and thus the torque curve. It uses a controller,
two-way vacuum switch, and a vacuum tank. 

The controller has a ground, switched 12V+, an rpm signal tap from the
factory Bosch ECU, and a two pin connector that it uses to activate the
two-way vacuum switch (that's connected to a little diaphram that opens
the flap in the manifold). The controller has an adjustable rpm set
point for the rpm opening point (adjustable from 2K-6.3K rpm), and it
has an adjustable hysteresis setting from 0-200 rpm. The best torque is
made when the settings are 4K for the flap to open (short runners, high
hp up top), and a 50 rpm hysteresis (so it closes at 3950 rpm). Works
VERY well when all is functional. Rpm set points are made by DIP
switches (8 of them). Test mode will cycle the switch on/off (set all
DIP switches ot OFF), and turn the LED from green(closed flap) to red
(open flap, and back...

The controller is done for. It will not even function in test mode. A
new one is $300. That's insane, for such a simple PCB. I tested ALL my
connections for continuity, and all check out. The wiring is sound, and
everything checks out. The controller will activate the two-way vacuum
switch as soon as it gets switched power. Regardless of rpm signal, or
set point. I looked at the PCB (encased in epoxy, except for the DIP
switches)and there appears to be a little discoloration or corrosion in
there. I'm an ME, not an EE...so I need a replacement controller.

I looked at my Summit Racing catalog (pg. 119 & 126)and found a couple
rpm switches...but I don't think any of them have a hysteresis function.
The MSD one has a "low" and a "high", but that's it. I need something
that offers me adjustability from 3500-4500 rpm, with about a 50-100 rpm
hysteresis. I don't want to fab a PCB, I don't want to spend over $100,
and I need something soon. Without a controller, I have to choose
between low end torque, or high end power (by having the flap closed, or
open all the time). Drive-ability is less than perfect.

So, does anybody know of an rpm switch that has an adjustable "on", but
also has a hysteresis setting too? Maybe I could get the MSD unit, and
set the "off" rpm set point lower than the "on" set point (an have a
negative overlap, making my own hysteresis)???? Thoughts?

Jason
'93 VW Corrado VR6 w/ failing Schrick VGi controller!!