I have a 1990 Jeep Cherokee. Almost a year ago we rebuilt an engine from a 1996 Jeep Cherokee, cammed out, headers, other mods. it has been running great for the longest time. Now after a short run to the store it hesitates to start. If I drive a short distance, a few miles. Then after I shut it off and try to start it a little later it cranks over for the longest time before starting It takes a couple tries to get it started. If the engine has sat for a long time, such as over night the engine will start up with in a second. This only happens after a short trip. Please help me out. Thanks