Fuel consumption is rubbish on my 1.9tdi Touran so I thought its slow to warm up lets change the thermostat, its not easy to get to the 10mm bolts holding the thermostat housing in place so I first removed the hose, lucky I have hose clamps for that job then found the top bolt is tricky the bottom one is very tricky, I'll say no more there I loosened the turbo hoses on the right side of the engine, on reassembly I test drove it and there was no power because the rubber hose seal had slid up its fitting so you couldnt get the clip on, I did get two codes One was the MAF sensor was outside its normal setting the plug needed pulling off and reseating there and the engine was under boosting, quelle suprise!!

Im wondering how much you can adjust the boost before it overboosts??

Anyone had a twiddle with theirs??

My Old Peugeot 306 was tweaked slightly from 11 to 18lbs of boost and a very slight tweak to the fueling, iy actually IMPROVED the fuel consumption and gave 45mpg instead of 42mpg.

I think the boost output is set on these engines, unlike the older generation engines where you could loosen a lockscrew and wind the settings up