135 tdci issues

[Slimsimonslim]

Hi everyone newbie here so forgive me if I get it wrong
Ok here goes 2004 transit 135t350 lwb medium roof rwd 6 speed tdci with 130000 on clock
I have owned it for the last 7 years with a few problems but for the last few years it has been fine
I recently decided to do some servicing myself as it seemed expensive to pay garage for a ten year old vehicle
So I replaced alternator pulley,aux belt,tensioner and fan coupling.that sorted the chirping belt which had been driving me mad for the last 3 years.
Then a new air filter went in and an oil change and filter was carried out.
All was fine for a couple of days so I thought time to give the old girl a bit of a blow out and ran her to 90mph with hard acceleration, straight after that it felt like I had lost some low down power(bit like boost hose popped)
Checked boost hoses and all seemed ok.looked into problem then decided to block egr which was a bit gunked but no better
Then cleaned intercooler and map sensor still no better
By this time engine seems to be pinking a little around 2500-3500 revs so tried cleaning maf sensor still no change.
Tried running the van with maf sensor disconnected and it seemed better(could have.been wishful thinking as I am starting to doubt myself at this stage)
Tried maf connected again and starting to feel a bit lumpy low down, disconnect maf again this time no better!
Had a mate plug in with Bosch diagnostic and it showed maf code but this could have been due to it being disconnected
Cleared the code and it felt smoother but still down on power then a few miles on it was back to being slightly lumpy and pinking
Then tried fitting a new hella maf still no change.all through this the engine starts as it always has on the first turn of the key and seems to idle as usual (rock steady,no hunting) and no smoke from exhaust at idle,mid range or under acceleration.
The power seems to feed back in at around 3500 upwards.
Have stopped using the van until I can get it into local Delphi specialists(TT automotive Loughborough)
Concerned it may be injector failiure but is this possible with no smoke from exhaust?
The fuel filter is not genuine ford and a new ford one will be going straight on as I now know that this is a no no on tdci engines(it must have been fitted on a previous service )the indicator on the filter is in the green
The service light has never lit on the dash since I have owned the van but servicing has been sporadic due to busy workload
No other warning lights have lit and only maf error showed on the Bosch diagnostics
Any input would be a great help and at least I can walk into a garage with at least some knowledge so as not to get ripped off
Cheers everyone,
Simon