16683 Boost Pressure fault code and question about Turbo, Exhaust, Remap

[BarnaBK]

I will try and keep it as short as possible. Apologies for this mix, its a bit of everything.

Hopefully admins will let me go, it would be a bit of a hassle to post every single question in a separate thread.

Its A4 B6 1.8T 2004 Limited Edition (if that means anything), on 145k miles, Stage 1 remap, previous mod history not very clear, but its obvious there was a few before I boughed it.

Had no CEL/ MIL, I just did a fault-code read as the car felt bit sluggish on a random day, like not enough boost, and this came up:

- 16683 Boost Pressure Regulation: Control Range Not Reached: P0299 (Maybe soft-Limp mode?)

After clearing the codes it felt good again and code didnt come back just yet (a week gone). I had this code about a few months ago, exactly the same situation.

Then I started digging:

1. The DV is metal type (not sure of the brand) the stock was replaced, the N75 is still the old one, looks worn, could it be the cause? Wastegate actuator? Or what else?

2. When stationary I read about 23-24 inHG vacuum, 25inHG on decel. Is this an indication of a good hose system for boost as well, or its not even related, I could still have a boost leak?

2. Wanted to check if I have K03 or K04, did hard pull test in 3rd, 4th, 5th gear, it starts boosting around 2700 rpm 16-15psi and drops to 13-11psi at 6000 rpm, then drops to 9psi at 6300 rpm, and just after 7000rpm its loosing it all (rounded figures).

Even though the boost pressure slowly drops, the power feels constant up to above 7000rpm, it pulls pretty good, is this normal?

If its K03, it should loose any boost at 5000-5500 rpm right? Is what I got a good /bad /ok pressure?

3. I am reading boost pressure from MAP sensor through ECU with an app called 'Thorque' paired to a bluetooth OBD2 reader.

Is this accurate enough?

4. In case it turns out I have K04 then probably I am not using its full potential (18-20psi max?).

Im still running the CAT and have the stock size downpipe (recently replaced it, so new bolts), then a wider allmost 3 inch pipes Powerflow straight silencer and muffler setup.

Could I set boost control in VAG-COM, witchcraft skills needed for it? Will just a de-cat /test pipe give enough flow?

5. Did any of you upgraded the downpipe to wider one, like 3 inch? Are there factories that make downpipes this size specific to this model? I have difficulty to find them in UK.

6. Had remap done with the coils and plugs that came with the car (stock), then due to ruff idle I replaced them to R8 TFSI red top coils and NGK BKR7EIX .032 .

Should I get remap again with new setup, or ECU adjusting for it automatically?

7. Would I need bigger injectors in case I can get more boost? I currently have the dark blue Bosh set '0280156065' (EV6ES).

Is this the stock injector that comes with our cars? How much support these injectors can give for future upgrades?

I would'nt go too crazy with mods, just sort of do it on the weekend cheaper kind of jobs for a bit more power.

Any advice well appreciated.

Thanks.