Mazda 6 Problems

It’s likely to be one problem that is causing all of the issues you mention. It needs a diagnostic check to locate the cause.

It is rated to tow 750 kg if the trailer doesn’t have any brakes, or 1600 kg if it does have brakes. The Passat diesel will also tow 750 kg with an unbraked trailer, but 1500 kg when the trailer has brakes. There are no major concerns with either of them.

The tyre guys are correct that carmakers set their pressures based on a blend of performance, economy, comfort and wear. Tyre companies generally advise that you run higher tyre pressures for better performance and economy, but that will compromise the ride comfort. I would run a higher pressure for the benefits to handling and fuel consumption. Make sure you rotate your tyres regularly, that will even out the wear over the life of the tyres.

It is believed that it will be released in Sept 2018.

It's hard to give you a definite recommendation, as most cargo measurements are in litres rather than floor length, but I reckon most mid-size wagons and large SUVs would do the job for you. 

Most of these have a flat boot floor with the seats folded, and likely have ample body length for sleeping. 

So Mazda6, Skoda Superb or Ford Mondeo wagons are worth a look, plus large SUVs like the Mazda CX-9, Kia Sorento and Hyundai Santa Fe. 

Don't be afraid to try them out for size at the dealers either. You'd certainly test out a mattress before buying right?!

We understand Mazda released a revised engine oil dipstick with a higher full mark. It also released revised software for the dpf operation that changed the way the self-cleaning function took place. If you haven’t got those updates I would be approaching Mazda to get your car updated.

No, not in 2004, but a four-wheel drive model, the MPS, was introduced in August 2005.