Intermittent boost problem

[joshstanvw]

Wonder if anyone has had the same I have a 1999 20vT with an updated ko3s turbo and it is stage 2 mapped to 230-240 bhp and most of the time it flies but today pulling out to make an overtaking manoeuvre it seemed to forget to boost felt like a 1.8 non turbo the boost gauge was reading around 5 or 6 but after that it seemed fine again pulling like a grain
Any suggestions where I should be looking first or should I not worry unless it does the same again as this was the first time it has happened
just one other thought I accidentally filled up with regular unleaded would this make any sort of difference as I have always run it on shell v power

[dom]

Scan for fault codes as a first step.

[joshstanvw]

I don't have a vagcom how much are they to buy or does anyone in portsmouth-hampshire have one they could plug mine into (I can provide hobnobs and redbull as payment lol)

[Wazzzer]

Shame you're over the water mate...

You can get boost related limp mode on the AGU, your boost may be spiking a bit too high for the MAF to cope with which could be the MAF or N75 playing up...

[Jin_C]

As Wazzzer said the AGU engine you have will put you into a temporary limp mode when it detects unfavourable conditions. This can be reset by taking your foot off the accelerator. However if nothing has changed it will do it again when you plant your foot again.

The issue with AGUs is that they are averse to throwing fault codes so there is a chance you wont find anything when you get it scanned.

On top of checking the MAF and N75 I would also check the diverter valve. If you have a 007p check if you have to old type piston which are prone to leaking and get it replaced with the new type (If you ask Forge nicely they will send one for free)

As you said it could just be due to the fuel. If it detected too much knock and couldn't adjust timings past the limit to fix it could have just put you into limp mode. Although this I am taking a guess at, I'm not an ECU expert.

[joshstanvw]

Well I have just filled up with v power and wow is all I can say feels like it is pulling a lot harder and smoother I will check the 007p but how do I know if it's the old style piston? Is there a clear difference the mad and n75 will also be checked but for now decent fuel seems to have sorted the old girl out thanks for the replies guys

[Wazzzer]

sounds like it's been tuned to the limit and is retarding the ignition due to lower octane fuel