Please help. Codes are driving me nuts

[Mike6]

I have as a summer car a 2005 2.5i with only 59k miles on the clock. It sits all winter under covers in my garage on a trickle charger and is pampered like nothing when it comes out in May each year.
Last summer the yellow EML light came on and my Creator reader identified it as Bank 2 post cat oxygen sensor with defective heater element. I managed to get both sensors (no point just doing the one) from Bosch. Try as I might I was defeated by access difficulties , my blood pressure lying under the car and getting enough pressure on the sensors to undo them. Bit the bullet and took car to my local garage whom I have know for years and are very trusted.
They had to burn out the thread on the old sensors as they had welded themselves in , recut the thread on the exhaust downpipe before they could fit the new ones. The garage manager who I have known for years did the job and said it was touch and go and he was happy with the result. All good for a couple of weeks and then the orange EML light reappeared with codes 2882 and 2883 DME:Mixture preparation on both banks..
Took car back to garage thinking that sensors might be letting in air or something and they had car up on ramp in my presence and sensors were tight and exhaust joint was all sound and manifold gasket did not seem to be leaking. They attached their laptop diagnostic and ran a few tests which showed an imbalance between bank 1 and Bank 2 and suggested I replace spark plugs and check out intake system for any leaks.
Over winter I replaced the spark plugs and stripped out intake system back to the infamous rubber boot, spray cleaned the MAF and removed and reseated the DISA. No cracks or any other problems, even the 3 rubber bungs on the intake were fine and not perished.
Fast forward to last week, car started first turn of the key and drove really well in the sunshine. Went for a longer drive a few days ago down to Brighton about thirty miles away after filling up with premium fuel, made a number of stops including for lunch and then evening meal at the marina. No EML light and I was beginning to thing it had been fixed when just before home the light came on again with codes 2882 and 2883.
What the hell can I do to diagnose the problem. Will Creator allow me to narrow down the problem , if so how (I am not that good with using it). Will disconnecting the MAF show me if that is at fault before I buy a new one. I dont believe in co incidents so it is strane new light came on after Oxygen sensors were replaced.
Any thoughts, help would be much appreciated .

[enuff_zed]

If there is an air leak then doing a reset sends the DME back to original settings. Then as air gets in it keeps sensing a weak mixture and adding more fuel. When it reaches its limit it puts the EML on.
So I know you've checked a lot, but initial symptoms still say air leak somewhere to me.
If you disconnect the MAF then the DME runs a back-up map. It will still take a while for the EML to come back on if it is an air leak.
If it is showing codes for both banks then it is almost certain to be a fault on the inlet side; it is only once you reach the exhaust side that it becomes two banks.

[j3nks79]

A smoke test on the vac lines would be my next step

[Mike6]

Thanks for comments . for both banks to be showing codes I agree it is unlikely both oxygen sensors have air leaks or for both exhaust joints to be leaking but it is strange these codes appear straight after garage struggles to get old sensors out.
Can anyone explain to me how to use the Creator tool to check exactly what is happening that might narrow down the fault ie could it be a dodgy injector not seating properly. I am reluctant to take car back to garage again as they were very thorough in rechecking their work.
If its the MAF then I dont think there is any way of checking it.
Car seems to run perfectly well, even when the EML is on but obviously dont want to risk any long term damage to engine.

[Mike6]

I will ask garage if they can do a smoke test. The only thing not checked is the maf and I don't know if there is any way of checking if it's at fault. They seem very expensive to buy so I wonder if anyone has a spare working maf that I could borrow for a fee.
Thanks