r/Nbmiata

Ever since I got the car running after my 99 manual swap this idle dip drives me insane everyday.
This just at idle in neutral.
Then while driving, when I shift into neutral it dips, and sometimes dips to low where the car almost stalls.
Is this a sign my base idle is off ?
In the mornings when I start the car for the first time and start my commute the idles hover around 500-600 then once cars warms it moves up to its normal 800-850.
For awhile I thought it was the fact that I don’t have a clutch switch since the auto harness doesn’t have a plug for one under the dash but I don’t think that’s the case.
Any help would be much appreciated!

99 has been running fine. Filled it up with gas recently. Went to get a burrito and did a brief roller coaster road then the engine started to sputter. Pulled over, engine died and wouldn’t start back up. Appreciate any advice. Love yall!

After a short Hiatus I have rejoined the Miata community, leaving it and selling my two previous cars was the worst mistake ever. Miata is always the answer