check engine light on after upgrade cold air intake. What can be done?

i only changed the filter and added a piece where the maf goes, left everything else untouched.

What does the code say, Lean. Double check any possible air leaks, and/or post the code.

everything is connected, no leaks, a friend told me i had to play with the distance between the throttle and the flow meter, any comments.

Distance from the mass air flow to the throttle is irrelevant. It measures the weight of the air not its velocity. Try disconnecting the battery. Negative first. Then connect the two cables together for a few minutes. Then hook them back up, negative last. That should clear the code and allow you to see if there really is a problem. If the MIL light comes back on we need to know what the code is so you can be given the correct direction Lots of Big parts stores read codes for free. An inexpensive OBD2 code reader could do it too and you'd be able to read codes on tons of other vehicles too.