95Q Pinging engine sound at 40+mph

[kevindanielk]

There's an intermittent pinging sound coming from my engine compartment area, but only at speeds above 40mph, with a slight increase in frequency with greater speed. It is not a rhythmic sound, just one or two pings every few seconds, but the pings do increase with speed. I drove the Q up to 65mph on the highway and placed the transmission into neutral and the pinging was still there. I even tried turning off the engine while traveling at over 60mph, but I still kept hearing that damn pinging, even with the engine off and transmission in neutral, while coasting at over 60mph. I tried jacking up the rear wheels and ran her up to 100mph, but there was no pinging.
That pinging sound is almost identical to, but not pre detonation, I'm sure. If it was, I would be experiencing pinging under wide open throttle loads, even at low speeds. It has me stumped and a little bit worried.
I was starting to believe it was a timing chain tensioner issue but being that it still pings away at high speeds, with the engine off and transmission in neutral, I have to rule that out. That's basically the engine not spinning at all but I'm still hear pinging.
I haven't had a chance yet to get under the car, to check see if it's something pinging on one of the front wheel. Due to the fact that it's not pinging when I try it in my driveway, rear wheels jacked up, I am leaning towards it being a loose suspension part or brake component.
Anyone else with a Q ever experience anything remotely sounding like this? My Q just rolled over 140k miles, always used 93 octane and fully synthetic oil for two years now.