If the trim is going to 35, that I think is as far as it can go so that just means that what ever is going on, the ecu can't compensate for it. Even when my engine was as its worst, it wasn't that bad!That's a very extensive reply Andrew, appreciate it!
I have no engine lights in dash (I'll check if it lights up on ignition key, hoping the bulb ain't deactivated lol).
I have reset the DTC codes several times - with the post-cat sensor connected, though, the LTFT just jumps straight to 35 regardless. And it does it as soon as the engine/sensor is warmed up, and without the STFT being at such high values previously. I'm suspecting it's doing this as maybe the post-cat sensor is showing values so much off that it straight goes for "maximum fuel trim"? 35 seems to be the maximum.
I've already ordered the NGK pre-cat o2 sensor (from autoscout germany, though - so expecting the delivery to take up to a week or so). Wondering if I should take out the injectors meanwhile, and send them to an ultrasound cleaning or not. Will think about it.
The hosings seem fine, for what I could see (checked the ones connecting to the throttle body - one with the sensor in-line as well, is it an air temp sensor?). The oil separator you're referring to is the one at the back of the engine, driver's side (UK) and towards the low end, right? connected to a.... pressure regulator was it?
Other than that, how do I gain access to other hoses at the back of the engine, and are there others? Seems tight around the area