Plenty of MFi RST running about perfectly happy with well over 200bhp.... Mark @ MAD does a fuel mod to the metering unit that helps with the fueling, also your 5th injector can also work as Oronoco pointed out.....

AFAIK it's not the bhp level that maxes the MFi system out it's how much boost you are running....

ie: I know a guy with a 1900cvh on MFi and only running 10 or 12psi thats 240ish bhp - the MFi can cope easily with that - but try and give it 20psi on your 1600cvh to get similar power then it's gonna struggle......

As said above - Karl knows his shit - give him a bell