Chevrolet Corvette C4
Driver was having some acceleration and knocking issues and it had been a while since I had replaced sparkplugs and wires so I had a"Professional" do the tune up. The so-called "professionals" used the wrong ignition wires. They were too short, causing one of the leads to be routed OVER and in contact with the exhaust gad recirculator... the result and very big mess. Fortunately the engine was off and there was no fuel feeding the fire.