My 54 reg peugeot 407 2.0 16v SE HDI 136bhp?

hello, when i bought my car the intercooler had been byped, which i now know all about, ive got the intercooler but havent got the hoses for it yet.Thought id mention this first because although the intercooler was as it was i could still feel the turbo working but recently after running the car for a while the performance is crap, it just feels lke an ordinary diesel without a turbo....has anybody got any ideas what could be wrong with my car please....thanks