Yes please thank you, so my M572 D0 is correct? It's not D3? Btw I'll try the closest to point to hide them all when I get back from work today.
If the M563 definition of the tool you are using specifies D0, then D0 is also correct in the M572 command. You can tell when pressure advance is active by watching the large gear of the Titan. You will see it going backwards slightly at the end of high-speed printing moves even when they are not followed by retractions.
ah okay, mines is M563 P0 D0 H1 ; Define tool 0, so yeah that's right then, just wondering because I can barely see the difference in small blobs (0.1, 0.15, and 0.2 pressure advance all tried),though I do see the large gear go backwards slightly, okay so I've turned off coasting, should I up extra restart distance then? weird thing is I'm not sure which one is causing the "underextrusion", but the latest I've tried (this is still with coasting on though) was -0.4 extra restart and 2.2mm retraction distance, and the underextrusion happened at the smoke stack. (with 0.15 pressure advance), though not as bad as before, but can see it.
I haven't yet found a use for extra restart distance. A negative extra restart distance would cause under extrusion at the start of moves that follow retractions.
Hmm okay, guess I'll just try increasing retraction a bit more again then. Btw since 0.1 to 0.2 didn't do much, should I try 0.3 Pressure Advance?
You might like to try the pressure advance test script linked to from this post: https://www.duet3d.com/forum/thread.php?id=3661#p32107. You should be able to run it with a low amount of retraction if you ignore any blobs at the end of the lines. Replacing your Bowden tube by Capricorn tubing may also help, by reducing the need for pressure advance and the amount of retraction needed.
Ah that post, I totally forgot about that xD. About the tubing, do you mean this one? https://spool3d.ca/capricorn-xs-series-premium-ptfe-bowden-tube/
Small update: 0.15 pressure advance, 2.4mm retraction distance and -0.1mm extra restart seems to be doing it for me. I know you said extra restart doesn't really work, but I notice just a little smaller blobs when I have -0.1mm, however maybe I should just increase retraction distance to 2.6mm instead?
I said I've never needed to use extra restart distance - but if it works for you, use it! Yes that's the tubing I meant. It's available from various sources including E3D and some of their distributors. Using it on my Kossel has enabled me to reduce retraction by at least 1mm.