'07 5.3(LMG) 90mm LS3 throttle body

Hey guys, just swapped out my stock 87mm throttle body with a 90mm LS3 throttle body instead of doing a p&p on my stock unit. Only issue that I am seeing is that the rpm's seem to hang a little when coming to a stop...say if I were at 2000rpm and let off while coming to a stop the rpm's will come down normal then around 1200-1400 rpm it hangs for 3-4 seconds, then slowly continues down to idle speed. I have not adjusted my tune yet, just trying to get an idea of what areas I should concentrate on. Attached is a log from today, ambient is high 80's F to low 90's F with a 60-70 percent humidity.

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Originally Posted by InTruckDesign

Hey guys, just swapped out my stock 87mm throttle body with a 90mm LS3 throttle body instead of doing a p&p on my stock unit. Only issue that I am seeing is that the rpm's seem to hang a little when coming to a stop...say if I were at 2000rpm and let off while coming to a stop the rpm's will come down normal then around 1200-1400 rpm it hangs for 3-4 seconds, then slowly continues down to idle speed. I have not adjusted my tune yet, just trying to get an idea of what areas I should concentrate on. Attached is a log from today, ambient is high 80's F to low 90's F with a 60-70 percent humidity.

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Look at Hymey's sticky on idle tuning. Its #1 :).

Took a look at the sticky and also have done some research. Yje delay/hanging around the 1200rpm is normal as long as it is not excessive. It does this to burn off any excess fuel before dropping down to an idle speed. Now here is the weird part...after a days of driving and logging at different times my issue of it hanging and a slight surge at idle are near gone, could this be from the MAF re adjusting airflow calculations? I was also looking at my tune, should changes be made in B1650 Max ETC area and other field regarding TB size? I know I didn't increase all that much in overall diameter(87mm to 90mm) but the bore is much smoother with no protrusions/bumps ;ile the stock TB.