I have a 1998 grand cherokee laredo....it runs fine except for when i stop it tries to die unless i slow down slowly...can't just come up on a stop it tries to die...also when in park and idling if i rev the motor to 1500 and let off real quick it tries to die out.....it has 4.0 in it....any help would be nice...also need to find exhaust manifold..mine has a hairline crack on one of the welds....