So I have a 2000 blazer 4x4 with 206k on the clock. My car will almost always have a choppy idle on morning starts as of about a year ago maybe more but it is only for a short period of time and never trips the dummy light. I recently replaced the cap, rotor, and wires this last wk because i had my #2 misfire code on for about 3 days. I now no longer have choppy morning starts. It runs and idles smooth as well as I can get 19-23 MPG city and highway. My question is I replaced the spark plugs probably less than 40k ago and used Autolite Double Platinums ($5 a plug) I also replaced the #2 spark plug this wk with another new Autolite Double Platinum since it was misfiring and was thinking it was building up crud (looked fine when i took it out tho). So should I replace my plugs after my ignition system being so worn? Or should i be good for a while longer, the plugs claim 100k durability. It always drove fine after a minute or so of warming up and as of now its running better than ever.

2000 Trailblazer 4x4
206,000 miles
Spectre CAI & Flowmaster Super 40

 

NGK rep told me that todays fuel destroys platinum plugs
I would change them all or at least check gap and at the point why not new plugs

 

Iridium