If you guys haven't bought a gauge yet, hold on for a few days. I've had the spa gauge in my truck for almost a year and it works great, but I'm about to install a pressure controler with built in gauge from SP diesel. Don't know the cost since I'm a tester but I would bet it could be had for a lot less than the cost of a gauge and pressure box combined, plus I'll be able to compare iit's accuracy to the SPA. I hope to get it put on this weekend. Oh yeah, it'll be stacked with a TST so we'll know about any compatibility issues.