I have some software and connector that allows me to monitor the engine and check codes.
I hooked it up and was monitoring the engine on the way to work today. I noticed several times that the long term trims did not match.
Trim 1 would read 5.7% lean
Trim 2 would read 1.4% lean

Then at the next update it would go back to 3% or so on both and hold for a few updates. Then it would go back to a different readings again. Then next update back to matching.

I also noticed on the short term that a lot of times bank 1 would be leaner than bank 2.

Is this normal or is this indicating a potential problem and could possibly be why my highway fuel mileage is around 17 to 18 at 74 mph cruise set.

 

74mph is probably the cause of your poor mileage. The rated numbers are for under 65mph I believe.

 

Actually the highway rating of 21 was achieved with the 3:31 gearing driving 48 mph on average.

 

you need to read a little closer. There is also a high speed test that is averaged in as well as NO where doe it say that the 3.31 axle was used

 

bank 1 and bank 2 are always going to be a little different.mine is the same way,i have been monitering using my dashhawk.the trims are the ecu correcting for minute differances inharent to all engines.as long as your ltft are +/-8to10% your good.