Recently I took a road trip, about 400 miles. On the trip home, I accelerated hard in 3rd gear. Soon after, there was a very strong smell coming through the A/C vents, A/C was running. I can't say for sure that it is the engine coolant, but it does smell similar to it. This happened once before about 3 months ago, but not as bad, while I was speeding up to merge on to a highway. And it happened again, but not as bad, 2 days ago doing some data logging. The only time it happens is when I push the RPMs to around 4k or more. It went away the first and last time, but the second time, on the trip, I could smell it the next day. I am low on coolant, making me think there is a leak somewhere, but I cannot find any sign of one. No wet carpet, no spots where I park. I have a Jet 180 tstat, and wasn't able to save all of it when I changed it, so it was a little low. Temps are good, staying around 188, using preset Diablo tune fan settings. I am not familiar with this new coolant, it's smell when it heats up, but what I'm getting through the vents is strong and nasty. Why would I only smell it at high RPMs, and wouldn't it indicate a leak?