When non second order circular (NSOC) signals are transmitted over time/frequency varying channels, classical linear equalization (LE) suffers from performance loss due to the signal's impropriety. For such signals, and signals corrupted by one single improper interference, it has been demonstrated that widely linear (WL) processing can enhance equalization performance. In this paper, we will study the limit of WL processing as a function of the number of interferers. We will carry simulations corroborated by analytical analysis and show that the performance of WL processing, in terms of bit error rate, decreases as the number of improper interferences increases.