Ah, ok I didn't realise that, will go down that route first then.

Thanks for all the ideas, as I said its just had a new fip and the injectors were pop tested. I think easiest next option will be a boost guage, cos everything else appears at first glance to be the same.

Yea tried satnav, its definitely not as quick, I've recently put a new fip on hoping that was the problem but its exactly the same, doesn't smoke, starts fine, revs cleanly just not as pokey .

I'm asking you redhand!

Is yours tweaked or standard tho?

My tyres are bfg muds 255/85/16

Previous owner of mine did have a recon gearbox put in and I don't know what from, is there a simple way to find out? Also would tyres really take almost 20mph off top speed?

Ok, i have a 94 300tdi 90, 79k non tweaked and my buddy has a 98 300tdi 98k non tweaked, Mine requires driving hard and tops out around 65 his accelerates really well and keeps going into the 80s!! Should there really be such a difference between the same models?

Well im officially bewildered! Fitted new fuel tank to replace the slightly leaking one, and the problem seems to have dissapeared. As great as this is I cant figure out how it could have caused the initial problem. If only vehicles were this mysterious!!

If thats just the bolt on rail, take em off and leave em off. Itll give somwhere for water yo drain out! I took mine off years ago.

When I did mine it was a pain in the arse to get the new one back in as easily as the old one came out. With hindsight I think taking the sill off may have assisted the process!

Thanks for reply, this problem suddenly started and not after any fettling, is it possible that previous tweaking (i kno that the fuel screw at top back of pump was adjusted slightly in may, not resulting in more smoke and all has been fine) has come undone of its own accord? Also did u have...

Update to this, checked wastegate today using airline and appears to be working ok, also blew air through boost hose and cyclone. The intermittent surging is still happening and I struggle to get over 60mph. Still hoping for a guru to help!

Hi all, daily im becoming more and more stumped! my L plate 300 tdi 77k has a strange vibration/wobble/retardation like a learner driver kangaroo which happens when stationary and when moving mid rev rangeish resulting in loss of top end and mid range UMPPH.., ive replaced lift pump, run...