Need a replacement catalytic converter for your 1991 Buick Riviera? MagnaFlow offers high-quality catalytic converters engineered for 1991 Buick Riviera sub-models and engine sizes. We combine efficient design and state-of-the-art manufacturing to meet or exceed required emissions standards. Select your 1991 Buick Riviera requirements and state vehicle registration to buy the best Riviera catalytic converter online that fits your '91 Riviera and meets your state’s emissions compliance.