Hi I am a new member to the supra mania and I'm having a confusion about my 7mgte. I have a 1988 toyota supra mk3 7mgte turbo.I got a new used block and head and swap the old parts to the new used one.The motor was done which was about 5 months ago it ran great.About 2 weeks ago the water coolant was geting low and the temp was high and its smoking white only after you drive the car and let it idle for about a min. The engines stock and it runs fine no smoke comes out when driving.After you leave the car over night,it starts perfectly fine around 700rpm no smoke but after its warmed up later steams out the exhaust a little bit.Then when you gas it puffs of white smoke would blow out of the exhaust and it would idle rough around 400-500 rpm and have like a misfiring, the white smoke would smell like strong burning antifreeze and stings my eyes a bit. It dosent seem to have a lost of horse power when driving,but when its idling rough I hear a taping noise like valves. I dont know if its a bad head gasket,bad valve seals,water pump,bad spark plugs or fuel injectors.I checked to see if theres oil in the coolant but theres nothing but coolant,checked the dipstick and its fine.I am running a Dex-cool prestone coolant and mobile1 5w-30w oil,on octane 91 gasoline.Checked the codes and it has a code 51 and 52.I think it all started when I poured more coolant in the engine when coolant was low and warm because I remembered it was the only time it first smoked white but it was only a little bit 1.5 weeks ago. Let me know what you guys think the problem is.