Iam in the process of breaking in my Magnum 91 4s. Ihave run 3 tanks of 15% already. On the second tank the return line from the muffler to the fuel tank popped off at the muffler fitting. The engine seemed to be running well before the line popped off. After it came off the RPMincreased and it sounded like it was running with alot more power. I ran it up and down the power scale a few times for a minute or two before Ishut it down and reconnected the line.
Why would the engine appaer to be running better with no pressure from exhaust to ffuel tank? And am Ijust imagining it is running better? Could it be that because i am running it rich without the backpressure it leans out some? Thus increasing RPM?</p>