Sicko-21

Hi everyone, i have a rx7 FC TII the last three times i took my car this happened: usual heat cycle and i went around; I stopped for an hour to talk to a friend and when I turned the car back on after a few seconds some white smoke came out of the exhaust (not thick) but the smell was a little sweetish, it continued for about 20 seconds and then stopped, I left and put it in the garage. the first thing i thought was a water seal fail but the smoke is not as thick as they describe. I also made the following checks: * with the engine cold I removed the leading spark plugs after running the engine 1 sec without EGI fuse and they were dry and good looking; * I tried the champagne test and I saw only one bubble; * the liquid level does not appear to have dropped and there are no visible leaks. * the car starts the first time both hot and cold and didn’t have overheat problem. The thing I will try over the weekend is to flush the cooling system because the previous owner left the rusty water.

So my question: is this something I need to worry about and research or can I rest easy?

My modifications are: custom downpipe with HKS catback, cluch fan replaced with two electric fans,DEFI pressure gauge,DEFI exhaust temperature gauge and COSO temp sensor.

Sorry for the bad English and thankyou.