Is it $125 from split second or did you buy it used?
Also, the BTM is there to pull timing dependant on boost pressure. The biggest place where timing needs to be pulled is typically at peak torque, but the BTM wont advance the timing after peak torque, which affects power.
I've personally adjusted my base timing on my jeep by cutting off the notches in the distributor and rotating the cap some. I used a timing light as well of course.. At lower boost levels, timing isn't all that big of a deal. You could just retard the timing at the dizzy and run a little more fuel and be safe. Just make sure the AFR is good.
I've personally always hated FMUs... But they are the cheapest method