Redlance88

Hey all, kinda new here and working on keeping my 87 going until I can get a second engine ready. The car is a former Auto cross car, with cold air intake, and large exhaust, , non turbo, stock ecu, and I think stock injectors, the thing is running crazy rich at idle but seems to run well in all other regards, I have a new o2 sensor on order and new plugs , and fuel filter. Is it reasonable to assume that the aftermarket intake and exhaust are adding to the situation. or do you folks think a new O2 sensor will allow the stock system to adapt and fly right? I understand that stock the second gens tend to run rather rich at idle any way but this is really really rich. other areas I may have overlooked? thanks guys.