hdi very slow revving when first started

[gavxud]

For the first 30 seconds I after I start my hdi it is very slow to rev and feels reluctant to rev ie whe you put your foot to the floor it takes ages to build revs ( feels like a car does when the cats collapsed or a baffle has collapsed) its got a 2.5" from the turbo straight to a 2.5"bore 13" long straight through backbox so almost completely unsilenced so no chance of baffles/cat collapse

No codes other than for maf being disconnected

It only does this for around 30 seconds after startup then revs clean and freely after that whether hit or cold (I know I shoukdnt rev it cold but was just to test if it was just a hot start issue)

Car is de egr, de cat, de centre box and straight through running a prosteve stage 1 map supplied to the previous owner around 2 years ago (106k miles)

Anyone shed any light , im thinking lazy lift pump but id have thought it woukd fail to start rather than start bjt not rev if the liftpump was at fault

[andywhy]

Lack of boost pressure could cause this. I recall when my boost pipe was left off it was very sluggish to rev.

[gavxud]

Revs perfectly after 30 seconds though ...strange one

[Poodle]

Could be something on the aux belt starting to get sticky, or the vacuum pump perhaps. Bit of an odd one tbh.

[andywhy]

Revs perfectly after 30 seconds though ...strange one

Could be as the turbo gets oil pressure it moves more freely thus boosting properly? Not sure, definitely odd though.