2.0 Tdi Juddering/misfire

Hi guys been on this forum quite some time lurking about in the 8L section, I've just recently purchased a 2.0 tdi 140 Avant with a BLB engine and have got a bit of an issue with it

I'm not shy to getting stuck in as have rebuilt my 1.8t a couple of times but dervs are a bit more of an unknown to me

The car in question



The issues that I'm having with it I'm pretty sure are all due to the same cause

It's quite often slow to start, occasionally idles lumpy and get a lot of juddering/feels like misfiring when driving which all seems to occur between 1500-2000 when part throttle

I've done some digging around and it's looking like an injector issue, I've changed the loom as the first port of call and today checked block 13 on VCDS to which I got this



This was done with the engine up to temp on the drive, although 4 stands out as the issue I was expecting the figures to be more vastly different and obvious to one being at fault as when idling it sat at around 0.50 with the other 3 at -0.25
I haven't tried checking these values whilst driving under load as the laptop battery has crapped out

What do people think? Is there any other things can check or do before commuting to buying and installing an injector

Thanks for the reply, even if not a massive help....they say its the thought that counts

Think im going to go ahead and order an injector to replace no 4 and go from there

Will post the results when I eventually get round to it