Piggyback controller a good or bad idea?

a remap costs £250 to £400 for a reason mate. They will do damage. Could cause ur car to run rich or lean and screw sensors and god knows what to ur ecu
 
Ok cheers...just thought as it goes onto the MAF sensor it may be ok but if it's going to cause damage il give it a miss
 
I am just wondering is it worth putting one of these on? has anyone else used one? do they damage your engine in any way? ive seen them cheaper elsewhere and for 20 quid seems reasonable even if you only get 5-10bhp?

http://www.tuningwizard.co.uk/index.php?main_page=product_info&cPath=66_152_671_676&products_id=484

I would avoid on an S3 engine, much better to get a genuine remap and release it's full potential. Saying that though, I've been running one of these boxes on my Passat TDI for 80k miles with no problems at all. They are more effective on TDI engines.
 
Check out how many unit they have in stock 999 ? hhhmmm something tells me they cant shift them :)