You're welcome. I was under the same impression myself until recently. If you really need a kick though, pick up some Robusta. It tastes pretty rough but has more caffeine than Arabica.
This definitely shook what I had thought was fact for quite some time. I found this article[0] to be quite informative.
That was a good article. The only other cause of caffeine variation I'm aware of is altitude. Caffeine is produced as a defense against pests, and since there are fewer pests at higher altitudes less caffeine is generated in that scenario. Coincidently, altitude is usually associated with higher quality coffee. The difference is negligible, so I guess my point is if high caffeine consumption is a goal just drink more coffee.
The charred rubber flavour is almost offset by the incredible crema. But it isn't and you will feel like you ate charcoal. It's an interesting exercise alright.