The K-jet throttle body is smaller because of the use of the idle air tubes. Most of the air flow at idle is provided through the IAC valve. I'm going to stay with the existing manifold and adapt an IAC to the manifold as opposed to the individual injector ports. The 4.5 throttle body sounds promising and if the IAC adaption doesn't give the results I'm hoping for will certainly be an option to consider. Thanks for the idea!