The next step up from our Performer Series® Carburetors is our Thunder Series AVS®. Designed and calibrated to deliver optimum street performance in hundreds of applications, Edelbrock Thunder Series AVS® Carbs are undeniably the most innovative and dependable street performance carburetors available today. Primary and secondary booster clusters offer the most accurate and up-to-date calibration available for today's fuels and octane levels. The Thunder Series' unique Qwik-Tune Secondary Air Valve allows for limitless calibration of the secondary circuit with simple hand tools while on your vehicle. It's quick. It's simple. It's effective. It can be easily adjusted - in seconds - to suit your application... no extra parts required to achieve optimum performance.