Hi, as far as i know it now uses an in-house engine based on a popular antivirus engine (i don't know what it is but it seems to be VirusBuster's). PCTools don't use the old kav engine because it was object-code and they could not modify the source-code and improve it or add new features. I love this engine a bit more because it's pretty fast

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[Edit]
I was a bit wrong.. Here's some reference:
http://www.pctools.com/forum/showthread.php?t=44703