Impressed with the fuel economy and per-formance improvements of the 2-V TBI Avenger, we decided to take the Mustang’s 289 to the next step and install the 4-V TBI Avenger (PN 550-400, around $1,999 street price) and test it as well. This required a manifold swap. We used a Weiand Street Warrior dual-plane intake (PN 8124) with the correct square bore mounting flange for the TBI unit. The manifold retails for about $150. Notice the extra port in the front water crossover, allowing us to transfer the water temp sensor directly to the intake.