I have a '94 Suburban with a 350 c.i. Bypassed the rear heat and changed the t-stat. The radiator and front core are a year old and everything was working fine except for a leaky rear heat (which is why I bypassed it). It takes forever to get to 195 degrees if it even gets there. Heat is lukewarm at best. If I hold the throttle at 1500 rpm while parked I can reach 195. As soon as I start driving the temp drops to 130-140. Anyone have any thoughts? Thanks.