[dsraven]

good idea on the test with wet streets, especially if you live where there isn't much rain because when it does rain all the stuff dripped on the road becomes like grease when it gets wet.
aside from doing some tests with expensive tools you don't have much for options besides ensuring it is connected properly at the master, ensuring it all works as it should and is adjusted the same at all 4 wheels (asuming 4 wheel drum), all the tires are inflated close to the same, nothing is sticking (park brake cables), auto adjusters work, etc. after that it is a matter of trying an adjustable prop valve to see if you can get things to work together.