I would like to know how long methodone stays in urine if there is no build up and you have to take a drug test 4 days later?

I don't understand what you mean by "no buildup," but...

Methadone stays in your urine for at least 1 -7 days depending on amount of usage and frequency, longer in the blood and forever in the hair.

I have read up to 2 weeks, longer than any other opiates

I go to a methadone clinic. I have been going for about 5 years. If it is built up in your system like it is in mine, you are looking at a week and half to two weeks in your urine and longer in blood. I have passed a mouth swab test after being in jail for only 6 days. Xanax, in my experience getting dropped at the methadone clinic constantly, if built up in your system can be there a week to a month depending on the person, metabolism etc. If only one dose is taken, you can pass a uds a week later. If you need a benzo to get by, but you also have to pass drug tests, Klonopin is the way to go. It does not show up on a drug test unless it has been taken in the 5 hours leading up to the test. Certain tests, such as ones given to pregnant women are the only one that can detect klonopin because they make those tests very sensitive because benzos are a category X drug for pregnant women. So if you are pregnant, don't take any benzos; it is soooo bad for your baby.