My car will not go above 2500 rpm unless I switch it to manual mode. But there is no code as of yet.And i'm not sure if it's limp mode or not.

By brake lights are also stuck on.

 

Probably the little rubber stopper on the brake pedal arm.
they get old and fall apart. Without it the brake switch won't switch off.
I fixed mine with a zip tie nub.
Ordered a spare stock one for the glove box frome Z1.
But the zip tie is still going strong.

 

This behavior does look like limp mode. Check this out, seems to be the same issue as you've got..

https://www.infinitiq50.org/threads/...p-mode.145247/

 

Either the brake switch failed (unlikely) or, the rubber pads rotted and broke (way.more than likely).

(photo originally posted by forum member Elco)

This issue is becoming more common as these cars are getting up there in age. Easy fix.
OEM p/n:46584-S0100 or "Dorman" p/n: 74015.

It will take longer to twist and contort your body to get up under the steering column and access the brake pedal assembly than it will to replace the pads. I would replace both and call it a day (whether you use the ASCD or not).

NOTE: if you are 6MT, there is also one pad for the clutch pedal switch. May as well replace that one as well, if applicable.