Never wait 100k to replace your plugs. NEVER!! Any good mechanic will tell you this. The threads (from the head) will come out with the plug if you wait that long.

When you do put the plugs back in, be sure to put some anti-seize on the threads. This will prevent the aforementioned from happening.

As far as the sudden surge of power, I get that with my car too. I assumed it was just the switch in duty cycle for the injectors. Any ideas guys? My car is non-VTEC, so I know that's not it.