2 issues, handling and a moody engine motorhome

[Motorhomemadness]

I own and live in the very wild motorhome, i call it the wild thing as its fooking nuts to drive, it never used to be like it its a tribute 720 sports x motorhome, I've owned 190 mph motorbikes and this van is like watching the steering wheel from an onboard camera in the WRC!! It was also remapped from 140 to 180 bhp to smooth out the power delivery and to fix a flat spot at 1800 rpm.

Have a few problems, one is a handling issue no one can seem to find, it kicks, on the right side, the right side makes a creaking sound and when braking over small bumps can hear rattling, weaves like mad in the wind which it never did when new. and feels like both wheels are doing their own thing. It's been in three garages, they can hear the noise but can't find the faults. the steering wonders to the left yet the tracking is straight. It had new bushes, and new brakes but no new lower arms, One garage did say one lower arm bush looks a bit odd but didn't think it's the issue. The torque steer is mental, being front-wheel drive, can't put the power down uphill without it spinning up in damp conditions, its always the front right wheel that has no grip even with new tyres.

They wondered if it's a weight issue on something that's not 100% right but not showing up when checked. in a garage?

Second is the odd power levels the engine puts out, it has days where the power is very good, 6th gear at 1600 RPM at 60 mph and I don't have to hardly press the throttle in the wind or not, it just wants to go no matter what, the next day the engine seems to struggle, power isn't smooth, hitting the power the engine holds back then goes, it sounds if its struggling. the guys who remapped said it sounds like the DPF filter may not be in good shape, doing the manual high RPM burn seems to never work, the cooling fans run often and not what Ford states at about 300 miles, more like every 50 miles. Its fuel range used to be 28-32 MPG with the remap. It now does 18-23MPG no matter how I drive it and the van is 200 KG lighter than a standard sports x motorhome, So would a decat work better?

[dumper]

The first thing that comes to mine is to much weight on the rear end / tyres or pressures /weak front and rear dampers or broken/ weak springs if there’s no play in steering or surspention.

[Motorhomemadness]

Yeah I get that, its rear suspension is a single leaf so is not really up to the job, wanted air suspension bags but they cost too much so was looking at helper springs.

What I didn't say, at slow speeds, if a make s shapes, side to side, turning right is fine but going left can hear rumbling and a slight juddering. When braking over small bumps can feel and hear something knocking. When driving over speed bumps there's that loud creaking noise and when the van has been standing for a few days and hitting rolling type bumps that creaking noise is far louder and stops after about 5 minutes. The steering over very small bumps dances from side to side very fast and then wants to settle to the left. when it was tracked they found nothing wrong apart from a tirerod and that was replaced.

I had thought this was a shock issue when the van hits bumps that cause the shocks to extend and then settle, but again this could be its bank end squatting causing the problems.

Its really hard to find a garage that will look at it due to its size. the van is about 200 kg lighter than a standard tribute, it weighs roughly 3 tons,