Hi all, my 2008 XB12SS went from running fine to bogging down when opening the throttle with sudden lurches in acceleration. Idling is fine. I had replaced the intake seals a month or so before and checked them with the spray test and they worked fine. Also did ground point cleaning at the same time.

Tried a TPS reset which made no difference.
Hooked up a cable and looked at error codes. Had AMC stuck closed error. The valve did look gummed up on the muffler, gave it a good clean, oiled the cables and checked the dc motor and its all working fine now but it made no difference.
Pulled the plugs and they did look fouled so replaced them and the their cables but no change.
Checked AFV value and it was sitting at 140 which seems very high.
Got myself a fuel pressure tester and checked the pump when primed and when running, value is sitting at 49 - 51 PSI which I believe is normal.

So now I'm a little flummoxed. I did find some grey sealant (or something) around the PCV valves and grommets which makes me wonder if the PO had a similar problem and tried sealing these up. There was a small amount of oil residue around the rear one and both the front and rear grommets do seem quite loose. If these were shot could they be the problem?.

Any other suggestions would be welcome. Really want to get her back on the road again!