Ahh, I'm glad you found the cause!!
I would go ahead and change those plugs a wires out. Don't be cheap on the plugs!!! Make sure to get a new set of Injector O-rings and when you reinstall them make sure to lube them. Failure of replacement could result in engine fire. Before you start take a look at all of your vacuum lines and determine if they need replacing. If so add that to your list.
Also, if you haven't changed the thermostat go ahead and do that seeing as how your system is already drained down. Of course the thermostat is optional.
After you got it all put back together, make sure you have bled all of the air out of the system. Otherwise air in the system could/will cause headaches down the road.
Let us know how it goes...good luck.
