Richard, the x-jet is a downstream injector, I just think it is way too far downstream. Your machine should work fine with its downstream injector on the washer but after the pump. The standard chemical nozzle that came with the machine won't allow you to put chemicals up 3 stories high. Read the following response to John.
John, think about why a chemical nozzle draws chemical and a pressure nozzle doesn't. It's low pressure versus high pressure. For each machines specs, psi & gpm there is a nozzle size that will give the rated maximum pressure for your machine. Example: 3k psi, 4 gpm uses a 4.5 nozzle size to achieve the 3k psi. As you slowly increase the nozzle size, the pressure slowly drops but you will still get the full rated gpm. Now on the other end of nozzle sizes, a lot of chemical nozzles are 40 or 50 which is very large and drops the pressure very low but still gives the full rated gpm. They have a fan shaped pattern and will not throw the chemical very far. By reason, there has to be a nozzle size somewhere between the pressure (4.5) and chemical (40 or 50) size where this change over occurs. This is where I spent all of the money buying many, many different nozzles and degrees. For the 3k psi, 4 gpm machine I found that this change over occured somewhere between a size 15 and 20 nozzle. Therefore I now use a 0 & 15 deg, size 20 nozzle for most chemical applications. The 0 deg will put chemical up 3 stories and the 15 deg will cover the 1st and 2nd stories. You can use a 40 deg in a size 40 or 50 for inside porches and other close up work. What I also found out through trial and error was that I would rather rinse with a size 10 nozzle instead of the 4.5. If my chemical has done its job then I don't need high pressure to rinse, but I still get the full gpm. I now use a 0 & 15 deg, size 10 nozzle for most rinse work. I think the 0 deg, size 10 nozzle throws water further than the size 4.5 nozzle. To rinse porches, close up and delicate items, I use a 40 deg, size 4.5 nozzle.
Sorry for the long response. Hope this is clear and helpful. Remember the nozzle sizes I stated are for 3k psi, 4 gpm machines. They will be different for larger psi and gpm machines.