Is there any way to tell by looking if an ECU has been "chipped" or upgraded. I bought my 1.8t used and am just curious. It seems to be a little fast for being stock and I have no way of contacting the previous owners. I'm the third owner. Is there anything on the circuit board of the ECU that is visually noticeable?

 

if you are 99.5 and ealier, then you can open the ecu and physically see the chip, otherwise no.. sometime tuning companies label the ECU as well.

you could also get a boost guage,

 

I have a 99.5 Is there any trick to opening the ECU? Any percautions I should take?

 

Remove the weather stripping and slide out the cover that goes over your brake fluid resevoir and battery etc. and the case for the ecu will be on the drivers side corner. Remove the screws and take lid off. You dont need to disconnect your battery as long as you arent disconnecting the ecu.