Can you post your fuel trims on relatively stock setups? My new (used) high mileage IS250 after a reset is showing -15% to -10% fuel trim right off the bat and I doubt that is normal. Before I did the reset the long term numbers were over 10% across the board. I'd like to compare with other trims to see what you are getting on your long term.

 

Did you pull the ecu fuse or the negative terminal?

The fuse pull doesnt wipe out the LTFT's learned. It just clears codes.

It takes about 15 min, or more battery disconnect to wipe them out.

 

I reset via the scanner, all trims went to zero.

 

Id like to see what others look like to I just replaced a fuel pump and I've put on headers and a full exhaust along with an intake and I messed around with different tube sizes and air filters and it's crazy how much the numbers will change and how the car performs

 

Yes I have a Bluetooth dongle and app on my phone. I noticed my fuel trims around -10 for both. Also noticed rotten egg smell after a hard pull, and some uneven acceleration from about 2000-2500 in 6th gear. So I ran a can of BG 44k fuel system cleaner and sprayed the MAF with CRC cleaner. Took a tank to notice the difference but it’s smoother on the highway and trims jumped around a bit but not over -5 or so. Smell is still present though.

 

At least FWIK my 250 performs best with just a drop in AEM filter. I've tried many intake pipes, and I always get bad lag. Stock intake paired with the AEM dryflow filter gives me the best results. If you still have your stock pipe try that, and see how the car performs. I always feel it always has the low end grunt back. Change the intake pipe the car hesitates, and bogs like crazy.

 

The diameter of the pipe will alter the air flow readings. Obviously a larger diameter pipe will make the MAF think there is less air flowing and possibly cause a lean condition. The computer will adjust but there might be some odd behavior in open loop.

-10% is not too bad. I think -15% is a bit high.

I do have a spare aluminum intake pipe I am going to try soon and compare readings.