Its a Toyota engine with 90k on the clock? its just breaking in!
The probablilty of it being a blown head is pretty slim. Unless you overheated the engine, or was running it really hard, I wouldn't really think twice. You could do a compression test yourself and if there are 2 cylinders next to eachother that are low, it may be a sign of a blown head. Another often symptom is oil in the water, or water in the oil, so just check that. (Your oil would look white).