LTFT - leave on or turn off?

[billiardcue]

Had my 2004 Corvette tuned recently, the tuner disabled the long term fuel trims.

Any thoughts on this?

What are the advantages or disadvantages?

408 cid motor with 236/244 cam.

[dvx]

From my limited experience: It sounds like he set it up to run open loop, most likely to improve driveability. I'm not sure about Corvettes, but when you put headers on an F Body it causes problems for the 02's, particularly at idle. Basically they don't work like they should and your swings from rich/lean will be slow which can cause surging and the trims never "settle down" but keep changing. The other issue for the 02's is your cam. It will be inefficient at idle, allowing unburnt oxygen to pass through, which will cause the 02's to report false readings. It will think it is lean and keep adding fuel causing it to be pig rich at idle. The downside to running open loop all the time is that your fueling will change with the weather since the 02's are no longer keeping it in line. You can solve this by running a custom OS.