I use a Mines Racing plug&play upgrade ECU on my CS with slightly modded ST205 engine ( 3" downpipe and frontpipe from Aussi, HKS silent hiPower exaust, boost raised to 1,15 bar using a Blitz SBC iColor specR boostcontroller ) and it does a very fine job at any time. Nice AFR and EGT results and no overfueling at higher boost.
I´m using the Zeitronix Zt-2 system with the optional EGT sensor mounted to the header and the optional boost sensor for the results reading and display. This system does a simulated narrow band signal output standart:
Together with an oil temp and an oil press gauge all I need to know about the engines wellness: