Hilux with Vs V6 & auto

[bpefi]

Hi - I am a mechanic but getting on in life & been off the tools for the last 4 years - I have never had much experience with engine noises in the V6. Red motor - not a problem... Anyway I bought this vehicle 6 months or so ago & its been a lot of trouble - Mainly as I do not know where the full mark is on dipstick (sumps / dipstick tubes are modified for the conversion) anyway it had a slight noise from around the rh rear part of the engine & it would go away if I had 6 L of oil in it & get worse when down - (motor came with a bad sump gasket leak) Switched it over to Castrol Magnetec 10w 40 & it quietened it down quite a bit & was really quiet. Then I took it into a workshop to get sump gasket replaced. (I wont go on about the other problems but they have looked after me) anyway I told him what I wanted in it & they ended up putting 20w40 in it (unknown brand) motor was a bit rougher & then started making a bit of noise again. So I took it back with other things & got him to change the oil back to a 10w 40. Since then its been getting rather loud so I change the oil back to 10w40 Castrol Magnetec again (nice & clean anyway) & it quietened down quite a bit - but its come back with a vengeance now (after my wife had a had a main hose pop off & overheated it) & really do not want to drive it - motor runs sweet & the noise seems to be up top. I have heard of the earlier problems with balance shafts - but nothing else. I would have to say lifter - only because it comes & goes but its sounding a bit more solid nowadays. I am thinking about doing an oil pressure test on it shortly as the first part of my diagnosis. I suppose I need to see what comes out of the sump also when I drain it. I guess what I am asking is what are common problems associated with the V6 in relation to noises. I tried to check timing chain by rocking the crankshaft back & forth & in a Ford xf any free play before you can feel it pick up the slack & start to drive camshaft would indicate timing chain - but there is no looseness at all. Any tips for testing would be appreciated as the memory isn't what it used to be. I think tappet covers off & check for free play would be next option - appreciate any help I can get here...need

Another problem is fuel economy on petrol (dual fuel) I have a Carman scan tool - cant find anything wrong at all. CAI is working well, air temp is down oxygen sensors seem ok - waveform is good - done the Oxygen sensor bad earth fix - I am running 3.7 ratio diff with a genuine dual map chip - (was bad even on petrol only chip) 225/50/16 tyres. Pulstar plugs - genuine leads & air filter with CAI. With petrol chip it would go into lean burn mode as you could see oxy sensors just dropping right down when hot on highway - thinking about the diff ratio & wondering if someone can do a tune & switch it to map sensor & take into account the diff ratio difference. Possibly re enable the lean burn function would be great also. I always have to have it in economy mode or its revving a fair bit. lock up torque converter locks in around 70k - its not real urgent as I run it on LPG mostly - never done a fuel pressure test but it doesn't seem to be running rich at all - could do with some advice here as well. Cheers