Years ago there was a company that cput out a fuel system just like the FASS.The idea was that it takes the air bubbles out of the fuel line,therefore increasing your horsepower and fuel mileage.When you take your truck and have it put on a DYNO,the fuel enters your motor form the DYNO companies fuel tank ,which is usually above you truck,and do to having a gravity flow,the fuel going into your motor has no air bubbles,so now the motor will show a high horsepower than when useing its own fuel system,this is also how the FASS is suppose to work taking the air bubbles out of the system,as was explained to me.If your going to spend the money for this,by the time it will pay for its self,you will have already traded the truck off.Just what ever increases horsepower,also causes less fuel mileage,unless you have a very easy foot.There are many tune-up options you can do,exhaust manifold,muffler,re-configure the ECM,all of which might cause you to loose the engine warantee.Its funny,if you buy everything that is advertized on these trucking shows,you will spend a lot of waisted money.For instance,Ive been useing Equal in my tires as a balancer for years.Well the last set of steer tires I purchased,had such a deal,I had Centramatics installed,and as suggested,had the tries balanced first.Believe me when I say,my truck after the extra money spent,doesnt run any smoother than it did with the other tires and no Centramatics.I get 200000 miles out of my steer tires,I guess i just fell for the hype