There are two types of pump/engine setups, depending which type you have will dictate how your pressure is controlled. First type is a unit which has an idle speed control, which will bring the unit back to idle when trigger is released. This type is most often used on electrical units and the more expensive gas units. The second type uses a governed top speed, where the engine is always running at top speed and does not return to idle. This type is used on most cheaper unit, which I think you have. I’ll try to keep this as simple as possible. I’m assuming that your unit is just idling, because there is no governor spring attached. When you install the proper spring, in the proper position, your engine will start and run a full throttle at all times. There should be very little speed change when you pull and release the trigger. The only time you see a slight speed change is just after you pull the trigger and the governor kicks in to bring the engine back up to governed top speed. I hope this helps.