sc310hp

Well when i first bought the car the previous owner said that the car burned oil but i drove the car from minneapolis mn, to michigan and i never seen it burning blue smoke until yesterday and it was while i was sitting at at stop light for a long time then when i went to take off i reved it up a lil and let the clutch out and for some reason i looked into my side mirror and there it was a puff of blue smoke that i could see cuz it was illuminated by the cars headlights behind me. When i bought it i wasnt really that worried about it but now that i have seen it, it looks horrible to have a lexus spewin blue smoke. Now i have never seen it going wot cuz that was when i was looking for it to smoke but it also does not smoke when idling which i checked too cuz that is the 2 times when i thought it would smoke. Now from reading around im guessing that it is the valve seals, i was wondering what u guys thought as i would have some info before taking it in and havin them tell me that i need to have my whole engine rebuilt. What does this sound like to u guys???? its a 1993 sc300.