I agree with Jim. If you cannot find the ready made ones, the pantyhose trick is perfectly acceptable. Actually, it much more "adjustable" than the premade ones! You can add and remove layers at will. I start with one layer. If I need a touch more gas milage I will add a layer until it gets past where I need it and the power seems to drop. Then I take one off. It works the same as gradually decreasing the size of the venturi with the added benefit of keeping dust out of the intake!