2001 Jackaroo 3.5 l choking when it shifts down on the highway

Hi,

My Jackaroo has started to play up this week. The other day, on the highway the Jackaroo started to struggle when it shifted down gears . I had a rooftop tent on the vehicle which was creating significant drag, the car was working harder than usual with fuel up from 14 l/100 km to closer to 20 l/100 km. Traveling at about 100 - 105 km/h the car sits between 2-3000 rpm. Going up hills when it kicked down gears, as the rpm jumped to 3-5000 rpm the car would surge/choke as if it was running out of fuel. No engine codes were produced and it was fine when it shifted back up and the rpm dropped. Intrestingly after it happened the first time I pulled over and check a few things. When I set off again the problem seemed to disappear for a while. Only to returen later and stop after i turned it off again...

I had filled up with 98 form near empty not long before it started to happen.

Any thoughts on what may be causing this would be greatly appreciated.



Thanks for the help



Breno