Loss of boost pressure '03 TD5.

Morning all,
More than a year ago I fitted the EGR replacement 'tube thing' and a pressure gauge in the air filter side of the intercooler piping. I was getting 15 PSI boost max. Thought I would gently wind the waste gate actuator back untill I hit the 'limp home' mode then back off a turn, leaving me with a very mildly boosted engine. All went to plan except the max boost I could achieve was 17 PSI, I was unable to force the engine into limp home mode as expected, so I left it at that. Where it has been running happily ever since. About a week ago I notice the power has suddenly dropped off and I'm only getting 11 PSI max.
I'm thinking leak in intercooler/plumbing or cat blocked/disintegrated.
Other than the drop in boost pressure and performance everything is running normally, no warning lights and operates in this manner from a cold start, so I don't think I'm in limp mode. No abnormal air leak or turbo noises.
Anyone had a similar problem?
Cheers,
Mike.

Wastegate sticking/stuck open ???

Thanks Shifty,
Forgot to mention, checked waste gate operation with bike pump and all seems to be working ok. Waste gate begins to open at 16-17ish PSI.
Thanks,
Mike.

Afternoon all.
Had a good look at my LandRover today. No obstruction in inlet tract, air filter good. Pressure tested intercooler and pipe work, no leaks, small amount of oil in pipe work though. Looked at turbo, no sign of scoring on housing, rotor has a bit of side to side play in it but no end float, does this sound normal? It leaves me with fueling issue or exhaust? Turbo is definitly quieter when driving, struggles to hit 70mph.
Decat pipe?
Cheers,
Mike.

Afternoon all,
Tested MAF sensor as described in manual, and it is faulty...replaced and no differance!
Replaced CAT and centre exhaust box with straight through pipes and all power and torque has returned and a bit more I think. Conclusion is a clogged CAT. I do find it a bit to noisy at town speeds now so may yet refit the centre box next week. Anyone else find their CAT a tad restrictive?
Cheers,
Mike.