Okay. I picked this 93 5.0 off an old lady with 151,000 (mild) miles. I have changed plugs, wires, coil, fuel and air filters and pcv valve. I have ran about 8 tanks of fresh 91 octane fuel through it. Question is this: I seem to get this smell of varnish (or the smell of bad gas burning) when I am idling. It's got fresh fuel for about 2,500 miles now. Friend of mine thinks it could be bad cats but it passed smog flawlessly and is not down on power. Doesn't burn or drip any fluids and I made sure nothing was burning on the exhaust. I am at a loss here guys