# Have tuning questions? Need tuning advice? Ask a tuner. **URL:** \ **Category:** Shift518 Automotive\ **Created:** [July 15, 2008, 1:59pm UTC](https://forums.speedlife.net/t/have-tuning-questions-need-tuning-advice-ask-a-tuner/237806 "2008-07-15T13:59:28Z")\ **Posts on this page:** 1\ **Showing post:** 78
**Author:** ![Celtic1982citleC](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/celtic1982citlec/32/6323_2.png) [@Celtic1982citleC](https://forums.speedlife.net/u/Celtic1982citleC)\ **Post date:** [October 26, 2009, 5:56pm UTC](https://forums.speedlife.net/t/have-tuning-questions-need-tuning-advice-ask-a-tuner/237806/78 "2009-10-26T17:56:18Z")
I don’t have a lot of RB motor experience but in general as you accelerate the mixture should lean out…you shouldn’t be going lean then rich then lean again. I wouldn’t personally be beating on a car running 14.xx AFR at part throttle, especially under boost. But again I’m not familiar with how RB motors are setup…given however most turbo applications don’t like to be any leaner than 12.0AFR > [@Questions about Cummins Diesel](https://forums.speedlife.net/t/questions-about-cummins-diesel/24885/2): > > I recently swapped in another Z32 MAF to replace my old one which was damaged by water. And now the car runs slightly leaner. Maybe around 12.0 @ WOT. But now at 1/2 the max boost (~5psi) the AFR is around 14 or so. Is that something I should be worried about? The car seems to run quite a bit faster. > > BTW-Motor is a RB25DET --- _[View the full topic](https://forums.speedlife.net/t/have-tuning-questions-need-tuning-advice-ask-a-tuner/237806)._