Speaking correctly a chip or to chip a car was or is to remap a car. Just in the older days you had to physically change the eprom ( CHIP ). wheras nowadays cars have obd ports which enables obd remapping. I dare say the chipping your talking about is these stupid boxes that plug into the loom and interupt the messages what the ecu is telling the car with false readings. Some make the car think its permnanetly in cold start mode which adds extra fuel which while probably minutely incresing power on some cases causes them to smoke an awful lot more and buggers everything up. These boxes are not worth the money in my opinion. Do it right . do it once. Get a propper remap by a specialist that actually understands what and engine does and doesnt need and wherew and when. Evolution chips being one for example. Not some shit on ebay that the bloke will come out and do for 100 quid.