I have a weird problem. When i press on the brake on a cold start the RPM jumps down a lot, and when the engine warms up it does the opposite?? what causes this?? I have a 98 HX 166k miles that i recently convert to MTX.

 

What is your normal idle rpm and how much does it increase (warm) or decrease (cold) when you press the brake pedal?

You may have a problem with your brake booster. Do you need to apply an large amount of force at the pedal to brake?