Why not a FMIC for the S4?
Several years ago, we were quite successful with a front mounted intercooler system for the S4 installed on the Blitzkreig Beast, holder of the fastest K03 turbo 1/4 mile record.
However, to fit an intercooler core that was larger than just the cumulative volume of both side mounted intercoolers, an RS4 bumper had to be fitted, along with significant modification to the radiator support. The amount of alterations required to fit a front mounted intercooler that had superior performance over dual side intercoolers practically made it a custom one-off installation.
In order to make a front mount intercooler a simple bolt-in design meant seriously compromising its performance characteristics, which we were unwilling to do. To fit behind an unmodified stock S4 front bumper, the intercooler core dimensions had to be reduced significantly. Extensive cutting of the front bumper was not worth the safety compromise in our analysis, given that the vast majority of our clients drive their S4s on public roads.