SO I tried to find some info on this have not found much but if there is any additional info please round house kit me to the face and point me to it.. thanks.
I got an 2005 RX8 MT.
just got your basic bolt on mods. header, Aem intake, Exhaust, BHR ignition.

Oil mods.
Mazmart oil pressure regulator
Prosport evo Oil pressure gauge, Oil Temp gauge, Water temp gauge..

I have noticed NO performance issues at all. Just changed out my spark plugs the other day and car feels really good and pulls hard with no stumbling or poor idle. Oil Temps and Water Temps stay normal around 180 degrees for the most part on water and 180-195 degrees on oil temp. (depending on how hot the day and traffic conditions)

When I drive I get 50~80 psi over 4000 rpm cruising at 3500 ~ 4000 range its about 40 ~ 55 psi range everything looks good as I am driving. but when car is warned up and I'm at a light it drops out to 0 psi. On start up (Cold) psi is high about 50 - 70 psi and as the car warms up at idle it slowly eventually drops out to 0 psi. When I bring my rpm's up to about 1500 - 2000 the psi shoots up to about 17-20 psi.

I remember when I first put on the gauge it was always around 17-20 psi at Idle and to be honest I do not know how long its been going to 0 at idle I look at the gauge Mostly when I'm driving to make sure its not dropped out or too low when i am on throttle. I do remember old RX7 engines having this problem due to a front O ring but I'm not sure if its the same issue on the RX8 engine. Any info on this what to look for??

 

If you really didn't have any oil pressure, even at idle, then your engine would be seized. I suspect a problem with your wiring or sender.

 

hahaha I saw that ... good job.. thanks for the info..

 

Most likely the pressure transducer.....electronic pressure gauges are prone to have issues with the sender after a while. Likely need a new one if you can get them by themselves