Simple flight planning data suggests the following. As I call it, back of beer coaster planning, but using real world data, not just some POH 1970's ROP stuff which would make it difficult.
Route 1100NM flown at low level thus small climb segment and then flown at a TAS of 165KTAS.
By low level, that could easily mean 3000-4000' to clear terrain and there is no primary radar along that track only SSR/ADSB so it would be invisible. To be frank, this could be police and media lies. They could have flown this at 9000' undetected.
Time is roughly 6 hrs 40 minutes, and this checks out with reports.
Flown at that speed which is far more economical than flat out, say IAS 150 knots, and flown with reduced Manifold pressure and RPM along with a lean of peak mixture, this plane could easily produce 50-55% power on each engine, burning no more than 35 LPH per engine.
Assume the flight was 6:45hrs that would be 472 (482 allowing for a short climb) litres out of a 537 litre capacity. That is almost 30 min VFR reserves!
Looking at real world numbers, from things I have seen with my own eyes, a 55 Baron at 10,000' with 20"/2500 and 26.5LPH per side will deliver 155 KIAS and TAS around 185kts. Even if they went lower levels and set similar or slightly more power, I can see them having 8.5 hours allowing for climb fuel.
That mission is not even hard if you know what you are doing. Even dopey drug runners could work that out.
https://www.bonanza.org/aircraft-ind.../baron-95-b55/
Best Regards,