my two bolt (air cleaner attachment) carbs have the black jets(?) on them, i have a set of 3 bolt carbs with the red jets sitting in storage. is there a big difference? my car is running great except it tends to stutter and sometimes die at stop signs unless i pull the choke cable to raise the revs. is this a timing issue or a lean/rich issue? or possibly both? the idle is great normaly, it just sputters after running down the road until i come to the stop sign. thanx.