S40 (New) Engine 2.0D : Weak performance

[Sidonas]

Hello lads,

I have a 2004 2.0D S40 (no DPF), which is quite obviously underperforming. I have driven it for 40k kilometres without much trouble but the performance is just not there. It starts well, idles without any trouble and overall runs smoothly. Fuel economy is satisfactory as well.

The problem with it is that it lacks power. I've tried to test it for 0-100 km/h and it takes about 13.5s to get there. There are a couple of things I've noticed that seem off:
1) it feels super sluggish at lower RPM (1100 to 1800);
2) the pull it gives after the turbo kicks in isn't as strong as what I've felt from 93 kW Auris or 100 kW Grandis diesels;
3) there seems to be no difference between flooring the pedal and just pushing it down to 40 percent, no extra power comes;
4) during extreme colds (-15C) it takes awhile to start and runs weirdly for 10-30s after it does. RPM is all over the place and there is white smoke coming from the exhaust. This one feels like some of the cylinders aren't firing, as it smoothes out eventually.

I have that little Bluetooth OBDII connector and the only problem it gives out is: P2683 Engine Coolant Bypass Valve Control Circuit High.

I've been reading through the forums and one thing that came up quite often was blanking the egr, therefore I have ordered a blanking plate and will do it as soon as it arrives. However, I was wondering if there was something else that I should take a look at? Could it just be normal wear and tear?