You can run check valves, no big deal.
Or, you can go standalone.
I'm running DSM 450's and an AFC set to 40% fuel trim, which modifies the MAP signal enough that the ECM never registers boost, and hence no MAP sensor error code. It's good for about 9lbs of boost.
Oh, and if you go standalone, the stock MAP sensor is only good up until around 12lbs. If you want to run more boost, you'd need a 3Bar MAP.