Differential architectures based on two injection-locked MEMS oscillators are a promising technique for high-end resonant sensing applications since they enable environmental drift rejection and high sensitivity. But properly coupling two M/NEMS resonators together is challenging. In order to eliminate drift, the resonators must be fabricated very close to each other and to be as well-matched as possible. To this end, both resonators and the circuitry can be monolithically-integrated on a single chip. However this leads to parasitic coupling and feedthrough, which affect the performances. This paper explains how, block by block, our architecture and our chip are designed to minimize these spurious couplings. The improvements resulting from the optimization of the ASIC are illustrated by simulated and experimental results.