Cartech FMU question
 

I have a friend's 1991 Miata turbo with a T28 that is running 8psi with a Vortech FMU and MSD BTM device, I am thinking of changing out the Vortech FMU for a Cartech FMU that I have lying around here for the last year, hoping to try to do some minor level of fuel tuning, however I cant seem to find the check valve.

Is there any downside or risk to installing the Cartech FMU without the check valve?

Comments are welcome, the long term plan is to go Megasquirt but this is a quick fix.

From the Cartech instructions:

"Check Valves
Two functions are accomplished by the check valve. One, the simple plugging of a small vacuum/boost leak. Second, vacuum is required to pull the pre-load spring under the center screw away from the valve so stock fuel pressures can be achieved under manifold vacuum conditions. The check valve white end attaches to 4" vacuum line, and the line plugs onto the 10-32 hose barb attached to the needle valve. This allows venting the boost signal for adjustment, but will seal under vacuum. The check valve blows off into the atmosphere, do not hook it to the manifold or anywhere else."

http://www.cartech.net/fmu2020instruc.htm

You should be able to use a generic one from the auto parts store. Usually found either with the vacuum accessories or in the "help" section.