Help BAD M.P.G on revived cupra

[tuneups]

hello right i have an 02 cupra with the auq and i blew it to peices last year (racing civic type R) i bought a new block (low milage) and basically had it fully rebuilt including brand new top end (valves etc etc) when i got it back the engine job was fine although there was quite a few odd jobs needed doing e.g, exhaust blowing allover, 02 censor gone, pipes under intake ruined etc etc i basically gave up but recently i went out an couldn bare to see it all covered in muck an moldy interior so i basically ripped all the bad bits off 02, exhaust pipe work, n75, i replaced all the above and got i running nicely allthough with 0.4 bar of boost so i changed the n75 for one of a passat (150bhp) and bought new maff, and it was agooden but now it seems if i put 10 quid in it to take it out for a run its gone in bout ten miles!!!! it allso feels slightly jumpy wen holding lower speeds round town, allso the boost hits 1 bar and then drops to bout 0.7 while booting it.

And incase it matters it has mayonase on oil cap from time to time but had the head checked its ok, and i dont have vag.com yet
and i tried cleaning the part of throttle body you can see from taking pipe of. with soft cloth and some carb cleaner it allso has not had new plugs in it for while
and it was sitting up for a year sorry to go on jus from reading previous posts i can see you boys like all the nitty gritty bits of info to make a diagnosis any way please help as i feel like im running a small cruise ship hahahaha (oh and no codes come up on a scan)

 

[bcstudent]

Not really going to be much help here, but I was wondering how many miles the engine had done when it blew up?

 

[kevlpool24]

Sure you haven't got a fuel leak

 

[t0m]

fuel leak? fuel pump? u had it mapped?

 

[tuneups]

it had done 150,000 when it blew and i do remaps so i have tried it with various setups and on its standard map and its just so heavy on juice and no there is no fuel leak. i read the trouble shooting guide jus thought someone on here migght have an insight or experience with simlar problems i jus cleaned the sensor on the intake it was caked in oil

 

[sambryant]

could be a boost leak, check the pcv setup for leaks, i found 4 in total on mine