I am extremely new to engines, RC planes, etc. I am a student studying a JetCat P100 for class and I am desperate need of help. I have been having issues with the GSU. I have been able to get the engine running, but the GSU will not let us set the RPM to what we want. It repeatedly says that "Values cannot be changed" on every screen of the "Run" Menu. We do not have a throttle receiver attached to the ECU, I was under the impressive that I could change the RPM of the engine just through the GSU without a throttle receiver. Do I need a throttle receiver connected to my ECU and what throttle receiver should I get? I am simply testing the engine, not putting the engine in an RC plane, so I am desperately seeking any advice for what I should buy/do?