This injector is the Stage 2 performance injector for the E7 VMAC I & II Mack engines. This will give an additional 25 percent for the 1991-'93 E7 300, 15 percent for the 1991-'93 E7 350 and 400, approximately 40 percent increase for the 1994-'97 E7 300, about a 25 percent increase for the 1994-'97 E7 350, and approximately a 10 percent increase for the 1994-'97 E7 400, 427, ('94 454). If these injectors are used along with the Blixxton-Mack module, a performance turbo kit can be purchased to improve the efficiency of the additional power, providing quicker responsiveness and greatly reducing the smoke that may be generated by radical horsepower increases. These are reman injectors requiring that the old cores be returned. CORE CHARGE: A core charge of $150.00/injector will be applied to your credit card account, if the old cores are returned within 30 days, you will get credit. Feel free to call our parts department at 800-891-8038 with any questions.