Well wondering if ecu's are plug and play as i found my last tdi's ecu i scraped, think it has a map on it as when the car was running it was faster than my current one, and both cars where 90 bhp's with alh engine codes. also when looking into a postal remap blacksmoke says they can lend a ecu while mines is being mapped, so i'am a little unsure now, can anyone help out ?

If its had Immo defeat and numbers match yes

So what would happen if i unplugged my ecu from my current car and put my old tdi's ecu in ? would i lose any data or codes ect.. ?

Unless the immo has been disabled it shouldn't start.

I just bought a remapped plug & play ECU from Lee Metcalf at MOT 7 in Hull. Came with the Immo disabled & EGR deleted for £95, car is running absolutely great, & I couldn't be happier. Lee is very helpful & I recommend him highly.