Integral gas engines represent a critical element in the US gas pipeline network. The stricter emission requirements now facing also these engines have prompted the question for advanced control strategies. Among them MPC has turned out to be a promising choice. Unfortunately, MPC has two main drawbacks a high computational and a demanding and non intuitive tuning effort. These issue become even more critical if speed and precision of the hardware is limited, as it is often the case in embedded solutions. This paper extends previous work on the control of such systems and concentrates on the latter issue, the selftuning. It proposes a tuning approach based on the well-known equivalence between MPC and a set of linear controllers as well as on the use of a mixed cost function which explicitly includes the numerical condition of the MPC problem. As the paper also shows, this yields to an impressive increase in the effciency and performance of the online algorithm by reducing the number of QP iterations necessary at each step.