1993 SL1 w/ 220,000 miles very high idle

My friend was in teh process of changing my spark plugs and broke a plug wire (i forgot to purchase new wires). Another friend had spare 7mm plug wires, so I put one of those on temporarily. After just replacing 1 wire and nothing else, my idle is way high. I am afraid to replace all other wires and plugs for fear of idle speed skyrocketing. I beleive that the previous owner may have increased the idle to compensate for a crappy exhaust job, which I have replaced entirely since, and crappy wires, plugs, and distributer cap. Is this a possibility and if so, can I adjust the idle speed down? Thanks in advance for help. :P