is there a need to tune for fuel at part throttle

[packrat555]

It is my understanding while the ecu is in closed loop it will automatically adjust for fuel except for when you are in a wot mode.

If this is true why should I bother adjusting for fuel if the ecu will effectively do it;s own thing.

[Spunkster]

You still need to tune it properly to that it is running close to where it needs to be in open loop.

[tricker_luke]

If the fueling isn't quite right, say up to +15% short term fuel trim, what problems might this cause? I've read people say short term should be about 5% or less

[Spunkster]

If it is off by that much then you should adjust the fueling to get it closer to 0.