My 2002 chevy 8.1l burns 1qt of oil every 1500 miles, no leaks found, but sometimes i smell burning oil, I have 45000 miles on it, Any Ideas??

They had some different intake bolts they were using on them to help with it but about every 8.1 uses oil.

My 2002 chevy 8.1l burns 1qt of oil every 1500 miles, no leaks found, but sometimes i smell burning oil, I have 45000 miles on it, Any Ideas??
http://www.jasperengines.com/pdf/8.1_Oil_Consumption.pdf