can the utec stop the cel light from coming on if you have catless downpipe? can you add in the utec program that the catless downpipe is on the car so it wont turn the cel light on?

you can turn the cel off completly, you can not tell it to just not report a certain error code.

what is the diference between utec and E-management (Gready)??

Also, if you turn off the CEL I don't think it will keep the code from showing up in a OBD-II scan so if you are trying to get around that you might want to try the resistor mod instead.

i just dont want the car to go in limp mode. can i use the resistor and the utec together?

Yes you can. I don't think the CEL condition would cause you to go in limp mode - you will just have errors in your OBDII log (also I have only heard of the limp mode in the 2003s).

The cat efficiency CEL that would be caused by the loss of a cat isn't going to cause your car to go into limp mode... The UTEC just keeps the light from being on, it doesn't do anything to the stored codes in the ECU or change how things that cause CELs might affect the car. For instance if something that happened to really make the car go into limp mode (which would trigger a CEL), it wouldn't prohibit that from happening.

I think that the UTEC actually handles the spark control. I wounder what the effect of a car going into limp mode would be? If the ECU took over fueling and boost, but not timing it might be a bad thing.