Which I assume is just a new casting of a factory head? If you have a better flowing exhaust, and bigger throttle body, and higher output injectors, you should in theory be able to flow more and and fuel through the engine and gain some HP. There's never any guarantee of that though. I certainly wouldn't expect any fuel economy increases. Whats your goal with the bigger throttle body? Just more power? Is the Jeep otherwise stock?
88 YJ with a 4.6l stroker, AX-15, NP231, 2.5" lift, 4.10's and 33's
2000 Red XJ w/ 350k+, AW4, NP231, Locked Rear, HD Crown Leafs, trimmed to fit 33's, soon to be a donor
2000 Silver XJ, Drivetrain from the Red XJ, Stiffened, IRO leafs, RE coils, custom 3 link, WJ knuckles, 35's <=== In the works