Idle dips under braking...sometimes stalls
 

Before someone goes about flaming, I sat here for over an hour reading old posts trying to find something similar and while I came close to the symptoms I'm seeing, the thread was all about three dudes bickering in the end...
So, here it goes. 6spd 04 RX8 with a replaced engine. Not sure when the engine was replaced, but the vacuum lines suggest that it was indeed replaced once before. The car currently is registering 92k miles, with what I'm sure about no more than 60k on that. There is a little bit of modifications on it, but nothing major. RP supercat (high flow cat) with about 15k miles on it bolted to a Greddy SP2, a BHR-like ignition using same Yukon coils and a good set of ignition wires, NGK Iridium spark plugs changed out recently too (tested, all fire properly) and a K&N typhoon filter.
So the problem is that when I drive for a bit, if I come to a stop and hit the brakes pretty hard, the car has a tendency to drop to about 750rpm's then bounce back up to normal idle. If i brake hard first, then really stomp it at the end, I can make it die altogether. If i brake gradually, none of this happens. Never did a compression test, but the car pulls very well regardless of RPMs and idles like a charm. I only have this problem at "spirited" stops. I saw a thread from the Australian colleges suggesting that it may be due to a disruption of the airflow around the MAP sensor with these big intakes, although I'm not sure how plausible that is.
If anyone had anything like that happen, I'd be glad to hear how you fixed this.

A lot of reasons could be associated with idling issues. Assuming that your ignition is good, your engine is healthy, no vacuum leaks are detected, maf sensor operates correctly and is not dirty, ess operates correclty and not dirty, etc. I would blame it on the intake and I would also check the motor mounts. My idle drops sometimes when I stop to about 750 rpms but I also know that my right motor mount days are almost done (about to change it in a couple of weeks so hopefully my idle will be stabilized again).

Yep, could actually be motor mounts, but also should start by cleaning the ESS, the MAF, and throttle body.......at least around where the butterfly valve comes to rest when closed. Hit the easy ones first.

Alright, guys. Will try cleaning all that tomorrow or Friday, Mazurfer. Tza0001, you reminded me about the motor mounts. I used to see the idle dips more often on my old set even without the hard breaking, but I recently replaced those. I didn't go with OEM mounts for replacement though, but instead with the RX8performance polyurethane ones...i wander if that has anything to do with this. Well, I'll give it a nice clean and report back. Thanks again, guys.