Brushcutters

i have an 545 rx brushcutter its new i have it for 3 weeks now. oil is coming out from the exhaust but not where the smoke is coming..somwhere from the back and the side of the muffler....oil mix is 50:1 soo not too mutch oil..i use ls+ and now hp ultra from sthil...in service they say i dont accelerate it enough... is that true? i use brushcutters fro 7 years never had this problem..