News: measured the fuel pump, looks ok. 3.5 bar on startup, then 3 bar then 2.5 bar at idle.

Also, because the exhaust gases smelled rich to me, I went and did an exhaust gases test. Conclusions:

1. At idle, they're fine.

2. At part throttle, they are VERY RICH, up there at the allowed legal limit.

Looking at number 2, gases very rich while the O2 sensor says they're very lean, tells me that the O2 sensor is shot. Before I go and order a new one (very expensive! :( ), does this look like a logical conclusion to draw?

ps: I've attached the actual test results, which the guy explained to me.

I'd want to have my memory on this confirmed, but if that lambda value is a voltage, it's very high (~1v), and should be about 0.7v.

It's not a voltage, it's the lambda factor I think, that is, how far the detected mixture is from the optimal mixture. The test was done by inserting a probe into the exhaust...

Ah right. In that case I have no idea what it means, but if it's an offset from stoechemetric mixture, check the lambda sensor voltage. As I say, I think that should be around 0.7v.

Far as I remember, I checked some vag-com group (don't remember which one) and at idle the voltage fluctuated around 1v, 0.9xx -> 1.0xx

later edit: checked again, the precat O2 sensor voltage fluctuates between 1.4v and 1.6v. The lambda factor fluctuates between 99x and 11xx.

Edited 29 April, 200917 yr by jmf

Any ideas where in Europe (but which ships to Romania, awesome doesn't for example) I can buy a 4bar FPR?

Does it need a 4 bar pressure regulator? according to you link on page 4 the TT 225bhp bam engine uses the 3bar fpr.

Have you got the injectors yet?

Well, before buying the injectors I thought I'd try a cheaper solution for increasing the fuel flow with the 4 bar fpr. Theoretically I would get a 15% increase in fuel flow, which might be enough to stop the lean code.

Ahh i understand now.

have you seen this

VW AUDI 1.8 20V TURBO - 4 BAR FUEL PRESSURE REGULATOR on eBay, also, Audi, Car Parts, Cars, Parts Vehicles (end time 08-May-09 01:52:07 BST)

Yep, already tried to contact the seller. Fingers crossed, thanks for the help

4bar FPR fitted, problem solved. Been running for a few days with mult trim at 6.5%, this morning it was 5.5%, so it seems all is well.

Also fitted a S3 TIP from Forge, which, being quite large, ended up strangling the combi valve vacuum hose, which resulted in a "sai: incorrect flow detected". I bent the metal vacuum hose a little bit and now it's fine again.

Another note that might help someone: careful when changing vac hoses that they're the same diameter. I changed a small hose which ultimately leads to the DV with a 4mm one (std is 5mm) and now I sometimes get a little bit of chatter when shifting. Ordered some Forge silicone 5mm hoses, hope that sorts it out.

Big thanks to everybody for your help! :balloons: