I dont know about the howell, but I think its based off the GM TBI systems correct? If so that is probably the starter signal wire. Whereever you hook it to the starter solenoid, make sure its only getting power when the starter motor is enguaged. The ECM gets a signal from that wire letting it know you are trying to start the engine.
79 Cherokee Chief 401/T18/D20, MPFI fuel injection, hydroboost, otherwise stock.
Future mods: Caddy 500/NV4500/NP205, HP D60 front D60 smooth botom rear, 5.13 gears, 35x12.50's on H1 beadlock wheels. Warn M12000 winch.
93 Wrangler 4.6 stroker/AX15/NP231,SYE,CV, OME 2.5 lift, front hub conversion/big brakes, 31X10.50's Warn M10000 winch.