Hi folks, hope you can help me, also sorry for the huge post.

 

Ive got a 2011 Octavia VRS and under part to half throttle the car will start to accelerate then suddenly feel like it’s trying to be held back, can hear the DV venting air then will suddenly accelerate fine again. Happens in any gear but usually between 2000 and 3500 RPM. Will happen all the time at 70mp 6th gear and part throttle and about 30mph 4th bear with part throttle. Sometimes it’s only a little bit but sometimes in quite violent and the car almost stops accelerating fully, but the Rev counter will still increase slowly and can hear the revs bouncing up and down. Full throttle seems fine so far. Only started happening after a stage 1 remap from Unicorn Motor Developments in Stockport who are a Porsche and VAG specialist with lots of good reviews. Have been back and they logged a load of stuff with VCDS and despite feeling it when we were out they couldn’t figure out what it could be. Have had it checked at AwesomeGTI and my local VAG specialist garage and neither can find anything wrong. There is no CEL and no fault codes. So far I’ve had an intake carbon clean and new injectors, cleaned and readapted the throttle body, changed the PCV valve, MAP sensor, swapped the piston type DV, added the GFB DV+, swapped to NGK iridium spark plugs with Audi R8 coils. There are no boost leaks found. Fuel pressure specified and actual are fine, the MAF seems fine and the intake manifold flaps specified and actual are fine. 
I’ve got VCDS so can log stuff but I’m completely out of ideas. All I can think of is for some reason the ECU is triggering the diverter valve in that rev range but I’ve got no idea why.

 

Mods are stage 1 remap from Unicorn Motor Developments in Stockport, Rammair intake, custom cat back exhaust, GFB DV+ and Audi R8 ignition coils,

Mmm. That's the trouble with EA888 engines, they are complicated beasts when they do not operate correctly.  I will have to review everything you said again, as clearly you have focussed on the usual suspects.  The diverter shouldn't be operating from 2,000 rpm should it. My instant reaction is a turbo problem, the wastegate bushings are not that fantastic on the IHI installed in stock.

 

What is your mileage?

Mileage is 61000. I was thinking the wastegate but the garages said the turbo and everything looked ok. There was no play in the wastegate arm when I installed the DV+ in September. Have looked at the Forge wastegate actuator as replacement just to try but don't want to be spending more time and money on what it could be :( it's really bugging me. The only saving grace is that I don't really drive in those gears at the RPM so can drive around it. It's just annoying haha. Seen a few people on MK6 gti forums with similar symptoms but no cause or fix.

How does boost hold up when the problem occurs. If you have vcds do some logging to include specified and actual boost when the fault is occurring. 

Requested and actual seen fine, logged the N75 as well and it's working when it happens. Was starting to think it's compressor surge but if it was would the actual boost be less than the requested? Can hear that text book 'flutter noice' associated with surge all be it not dead loud 

Im having the same issue but not as bad as yours as it only incurs in 4th and 6th at the same rev range.  I installed a GFB+ and that has helped. 

When you went for the remap, did you get a RS4 fuel valve and different MAP sensor installed?

Ive bought one and will be installing it soon.  Ill let you know it makes a difference.

 

Also if you are still looking for a Forge Actuator, Ive got one and will let it go for much more reasonable price than Forge!

 

 

Didn't get the RS4 fuel valve or MAP sensor. Got no idea about the RS4 fuel valve to be honest. 

 

Not sure about the actuator at the minute, want to make sure I know what's going on before trying more things. 

 

Be earger to hear if the fuel valve helps you out though. It seems to he a relatively common thing but no one can say for definite what it is