My information on this is just from reading the posts here over the last couple of years. Having said that, the 170 code usually means new MAF is needed. No you can't clean it. Well you can, so then when you replace it it will be clean when you throw it away... Misfires are usually code 300 or 302. These are sometimes from the spark plug connector(s). I suppose whatever the trouble is could cause a rich condition that would heat up the cat. Hopefully the experts will chime in now!

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra