bens97tbird,
It sounds a lot like head gaskets. It's hard to diagnos from a keyboard though. If you dare driving it, get it to a good mechanic's shop. They can perform a chemical test on the coolant that checks for oil. If you're getting exhaust in your coolant (sounds like you are) then chances are very great that you're getting some oil in there too. If driving is not really an option (and I don't really recommend it) then call the shop and find out how much coolant they need to do a chem test on it. Then you can just take a sample in to them.
At this point, I'm guessing that it is a small leak in the headgasket. This "hole" opens up significantly on the burning of the air/fuel in the combustion chamber. Under load, the car puts more air and more fuel intot he combustion chamber creating a larger explosion. This is why you only see it under load at this point. It will get worse and it probably won't take long. One thing also to consider if it is the head gaskets is your O2 sensors and catalytic converters. Neither of those like coolant and if you get enough dumping into the exhaust, chances are that you'll need to replace them. I say, fix the problem now, then if you have CE light and/or the car is running warmer than usual, you should go ahead and replace the O2s and the cats (with high flow replacements). Just want to let you know to expect something, although if you have caught the head gaskets soon enough, those things will be fine. Just don't be surprised if within 1k miles, those too need to be replaced.