I have level 1 file based caching enabled.
One thing I tried, which has yielded good results..
I've disabled our SMF Packs Shoutbox plugin.
We've had two little spikes into "very high" very briefly, but that's it.
We used to be hovering in the very high range with peaks into "extreme".
It might be a coincidence, and I guess I could verify by turning it back on, but I don't want to be shut down again
Image proxy is off. I had read about the https issues so as we're running https...off
In my experience, CPU spikes are typically caused by crawls. Look at your web logs and determine who the culprit is. Somebody hitting your site several thousand times an hour isn't hard to spot in the web logs!
If it's Google, throttle them in Google webmaster tools.
If it's someone else, block them.
As noted above, I use Hostgator. It may also be that Hostgator is squeezing their users. That is almost certainly part of it. For whatever reason, crawls didn't bother me in the past, but they do now.
I'm still on the fence whether to leave HG in the future. On the plus side, I have never had issues with uptime or support - they've always been rock solid. But on the downside I really don't like their backup policies & pricing. And I suspect they are squeezing resources - as shown by sensitivity to crawls.