Ok couple of points to make first

4.2 supercharged 130k.
LPG converted BUT not currently in use.

I have also reset the adaptations.

Right so what’s happening? So I plant my foot on the floor and it’s smooth up to 4-4.5k then it shakes and there no more power like it’s out of fuel, and it’s stinks.

I then let the revs drop back down and it’s fine.

I have no faults… any ideas? Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Blocked fuel filter would be my immediate guess....  Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

I’m not saying you’re wrong - In fact it’s a good shout but playing devils advocate, why does it run nicely the rest of the time? Only partially blocked?
Also shouldn’t I be getting fuel pressure faults then too? Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

You need more fuel at higher revs, it can't supply enough...

You would think it would throw a code but I have heard of numerous times when it doesn't...

It tends to be more common on diesels because of the bacteria that grows in it if left for a period of time...

With no codes and the symptom you describe I'd change the filter and chuck a bottle of BG44K in it to start with, pretty cheap fix if it works...  Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

You say it stinks? in what way?

A blocked CAT can give off odd odours and it fits with you symptoms.

J BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

Our local specialist told me that it’s quite common to see melted cats on the 4.2’s.

Can you remove the lambda sensors and stick an endoscope in to see what the internals of the cats look like? It should be a find honeycomb but apparently it’s not uncommon to see a molten mess. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

That would be incredibly annoying as I changed both last year for low mileage used ones - good idea I have a scope it’s going to get bushes tomorrow so will check over the weekend .

I do have a cheap cat for one bank not blocked but occasionally threw a cat fault so if it is that bank it would get me out a bind I guess Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

So a little update here i went into the tank and was about to change the filter and or pump I pulled the filter and there is a T for the lpg fuel return - normal… but there was some crap wedged where the bore changed for the T … this would be restricting at higher rpm/load I imagine. I’ve ordered a bigger bore T Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

If that smaller bore is designed to be the restriction for the fuel return to satisfy the lpg requirements, you will probably have opened another can of worms unless you have another restricter in the line.

Already thought of that there was a restrictive screwed into the Tee which I’ve moved into the new Tee Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Right little lunchtime update… but the new T in with a nice big bore so no restrictions (except where required!)

Cleared the adaptations and went for a drive it now drives nicely until 5300-5500 and if my foot is flat down I get the juddering again but I had the window open today as it was hot and it sounded like I was getting pop from under the front of the car while this was happening… any ideas Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Where was the popping noise coming from?

If it sounded like it was at the front of in the exhaust it could be a backfire causing it to pop. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

I’m not sure maybe the cat or maybe the engine - didn’t sound like a exhaust pop you can force.

I think just to rule out the fuel return as I’m not using gas right now I’ll cut the return out for testing. Will clear adaptations and do this and come back later Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

My car has an electronic fuel return fitted. When it’s not on LPG it cuts the power to the solenoid so there’s no fuel return. Is yours similar? If it’s returning fuel constantly you will have low fuel pressure. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior