This study presents the computational fluid dynamics (CFD) driven design and optimization of an intake manifold for a high-performance, restrictor-limited single-cylinder engine. The primary objective was to minimize pressure loss and maximize airflow velocity under the stringent constraint of a 20 mm inlet restrictor. SolidWorks was used for modeling, and ANSYS Fluent was used for simulation. The designs were tested at mass flow rates of 0.0732, 0.0852, and 0.0952 kg/s. The results showed that Design Model 5 performed better than the others, achieving airflow velocities of 220.6, 251.4, and 281.2 m/s, which is 4 to 9% higher than competing models. It also reduced pressure drop by over 69% lower than the other design models, measuring 572.02, 725.49, and 862.48 Pa for the respective mass flow rates. Mesh independence was confirmed with a 5 mm element size, and validation against previous studies indicated less than 0.2% deviation in pressure and velocity predictions. The optimized design’s strong performance stems from smooth airflow with minimal vortex formation demonstrates a significant enhancement in volumetric efficiency for restrictor-limited engines. This study provides a validated CFD framework for designing high-efficiency intake systems under strict flow constraints.