lean on decel
 

Car is EFI most you guys no. I took my intercooler off and put back on and now when I give it some boost , after I let up on the throttle my A/F gauge gets buried on lean and I get the popping out of my exhaust. It never did that before. I checked all lines and all tight. I cant find any vacuum leaks. I took the intercooler off to try venting my blow off valve to atmosphere and thats when it started. I went back to venting the blow off valve into intake and still does the same thing. Thanks John

If engine fuel delivery goes to idle value but the engine is spinning down, the pistons are pulling air into the engine so yes, you will have a lean condition. It's not hurting anything since the engine is not under load.
I have CIS and my car does that if I take my foot off the gas and let the engine turn over.

It is most likely set up for overrun fuel cut. That means if TPS sees closed throttle, ECU cuts fuel, both for economy and in order to not flood the cat with fuel. Also during shifting, revs drop faster with overrun fuel cut.

Mine is also EFI and does the same thing. It's not an issue.

If the engine did not go lean on decel prior to the IC being removed and replaced, but it does now, first thing is to double check all the connections you had to touch to accomplish that work.

Also, may want to check your TPS sensor to make sure you did not bump it or slightly move it (enough to throw off your TPS setting). TPS switch is likely mounted on the intake butterfly just below the IC neck.

In your TecGT software, you should verify your TPS closed setting matches the actual close of your throttle, plus a margin your tuner added to ensure the software considers the throttle is closed prior to it actually being on the physical stop.

You also want to check to makes sure your TecGT software setting is set to shut off fuel on decel below a certain threshold (set by your tuner). If this setting is on, the engine will stop popping. If the setting is too low, the engine will pop as it decels until it hits the set threshold then it will stop.

But, that will not fix the lean setting itself, just compensates for the lean setting by shutting off ignition on decel. If you really want to fix the lean setting you will need to go through the process of making sure you did not introduce a leak, then make sure no software settings have changed (they should not have changed).

Thanks.

My Tec3r has a decel enrichment area. I just turn it off and car stays fueled on decel.