classic c15 freightliner 2006

does any one know were i can gt some donaldson mufflers and muffler guards have any one hv good or bad things to say before i buy them thanks for the info....

 

i hv done a little research on them i was hoping to hear of some one that already hv them . is there a diffrence from a stock muffler and a donalson muffler im new to the trucking industry dont have much exper.. but i do own my truck 2006 freighliner classic cat engine c15 twin turbos .. its a piece of sht... bad power .. poor mpg.. and its breaking my wallet badly.. any suggestions .. i hv change fuel filters oil filters air filters all the boost hoses and clamps check for loose clamps and hoses i gt abt 5.2 mpg or less .. if any one hv any ideas to better my mpg . i hd hrd that changing the stock mufflers for some donalson mufflers will inprove mpg.. i also hv that e.g.r system . wich mk even worse can some one help .. any advise is greatly appreciated thank you......