In 50% throttle load/open loop no the ecu doesn't know what's going on with regard to fuel issues or corrections. If the fuel pump is compromised on proper delivery for a safe afr, the motor suffers.

 

it probably felt like it was running GREAT, lean makes more power... but of course.. lean is dangerous

and what junky said ^

 

Up to a point, and then it makes less power and then you burn things up quick from there. Running lean best is always the goal/target, problem is you cant safely keep it there because conditions change. A good tuner will see where lean best is, and then enrichen for safety margin. Generally goes for timing as well. Too much timing you lose power and you detonate, not enough and you lose power and you get pre ignition from high combustion temps.

 

I didn't notice more power. It actually felt a little sluggish. But that is in the past. The motor was in really good condition until it decided to eat two exhaust valves. In any case, I wanted to share my findings in the hope someone will learn from it.