The Pro-Flo XT LS1 EFI intake manifold is engineered with a large plenum and tapered runners to deliver maximum horsepower and broad torque band throughout the rpm range (1500-7000 rpm). Features include a 90mm throttle bore opening and 2.75" port exit height. This manifold produced 30 more horsepower over a stock LS6 manifold at 6500 rpm. #7139 Accepts Pro-Flo XT throttle body #3869 or adapter #2737 and standard LS1 throttle bodies. #7140 (LS2) accepts GM OEM 90mm or Edelbrock #3869 throttle bodies. Compatible with LS1 Fuel Rail Kit #3629 (sold separately).