Originally Posted by jchammond

Does your Z fire right up (like when new) ?
I read back through the thread & seen 160k on it...with the poor quality gas these day's-you could have an injector or 2 dripping after engine is switched off.
I'd try some old school stuff; after driving & letting cool down somewhat-remove spark-plugs & read them,,,also look down in cylinders with a scope.
Your A/F sensors may be getting tired also.
How's fuel milage,power,oil consumption ?
Get a good tech to ride along w/a graphing scan tool & record it.....something is bound to pop up.
Any extra information is helpful.