I originally got a Unichip only on my vehicle and was in the process of getting a retune as I thought I had a problem with it. Turns out the was a problem with the factory chip and an intermittent fault on the firing of all the cylinders. The guys at Dynomotive were outstanding as they had to take it back to Ford to get a new factory chip. It was still under warranty (I was actually in the last month of my warranty). They told Dynomotive to take off the exhaust and the new air filter as they said that those two items would affect the factory chip (yeah sure). It went back to Ford 6 times in total until they could not say any more and then (unfortunately) they said to the guys that "we know you have had a chip on this car but we can't prove it". the only reason was that by oversight the guys left a dyno chart in the glove compartment. Ford then left it on the seat when they picked it up just to prove they knew. So my experience is that with a unichip at least, as it leaves the factory chip alone, they seem to not be able to detect that there has been an additional in-line chip on the engine.
