There are piggyback units out there that will allow timing adjustments. But, simply using an FMU is not going to help in Closed Loop operation since the O2 sensors will simply tell the PCM to pull fuel from the injectors putting you back up at a 14.7 AFR.

Most piggyback systems rely on bigger injectors at a stock pressure, then fool the PCM into thinking it is under less load than actual by skewing the MAP or MAF sensor readings. By the way, you wind up advancing timing through the factory program when doing this, and generally not when you want it to.

Using an FMU along with a unit that can alter the O2 readings when in part throttle boost (closed loop operation) to get richer fuel mixture, then rely on the FMU to get your fuel mixture in Wide Open Throttle (WOT) conditions is about the cheapest method. Not perfect, but it can be done, and get some decent gains from a moderate amount of boost.

In theory, a SRT-6 PCM and injectors would work with a Turbo running similar boost levels, but, the SRT-6 uses an electric clutch on the supercharger, so it only comes on under certain conditions.

If those conditions are related to throttle position (I have not checked the operational parameters) versus sensing positive pressure in the intake, you could have some serious part throttle boost issues with a turbo running lean on the SRT-6 program.

Mr MoPar