Exactly. My 05 GT does this sometimes, and when it does the engine seems to produce much less power.

 

The less power is the knock sensors pulling timing. My ride today felt very nice with no ping. My concern is why is my stock GT not liking 87

 

Mine rattles real bad on a cold start up. I am not sure it is the engine pinging though. I think its more of something being loose under the car. Exhaust hanger or something. It only happens on mine at around 3k-4k rpms.

 

You won't hear a ping unless its under load. Your issue sounds like a heat shield to me.

 

If you have 50K+ on any car, you need to either clean and/or replace the spark plugs. The 100K B.S. is just that, B.S. The newer stangs (05+) are notorious for build up on their plugs. Pull em, clean em/replace them, and put them back in. Problem will probably be solved. Chances are there is buildup on the plugs and those areas of buildup are hot spots that can ignite the air/fuel mixture before thesparkplug actually fires.

There was a guy that worked for Ford as in FoMoCo not just a dealership that said the plugs in your cars should be cleaned every 10K because of this buildup. It was even released to the dealers as a service bulletin. Not a tsb but as an update to their regular recommended service items.

 

Well the car ran great last night with 93 octane in the tank. I'm beginning to wonder if the previous owner might have had the ECU modded. Any quick way to know.

 

^ great info on the cleaning of spark plugs, i think we have something like 25k on our 06 - i guess i should give em a once over just for the hell of it