@Grahf I seems to remeber I already tried with MODE 1+3 (with some of the last revs, not 1353) but I'm not sure. I'm going to test, hope it will work for me too.
Yes, actually I tried MODE 1+6 before. It seems that even the intro music is clearer, I was about to report it, but eventually I thought it was just a placebo effect, since it doesn't solve the main menu sound issues for me
First time I tested it now, very carefully, it seemed to actually solved, but after 3/4 secs I could hear the first imprecision. It is very random, sometimes it plays for a few seconds just perfectly, then on the next reset, issues start just at the beginning…
Maybe there is a slight improvement (maybe…), but the problem isn't definitely solved on my end.
Mode 1 solve the namco stuttering at least (small consolation).
Mode 1+3 fixes it only for iHDD. The game will always stutter through SMB and USB because the bandwidth isn't there. Personally, I would add Mode 6 just in case. I know sp193 worked on IGR and it's much better now, but I will never really trust any extra features to be fully compatible with all games.
I keep thinking that the blanket is just too short. A modification that make one game to work will probably cause problems to Others… MODEs are still really necessary.
P.S. I tried other combinations too: MODE 1+3+6, MODE 1+2+3, and some DMA combinations (like MODE 3+MDMA 0, end so on…).
@Tupakaveli I'm happy at least you solved, however it would be great if you could test the original CD game still. Since it's really weird that from DVD the problem is present.