Problems at >3000 RPM on motorway

I had the sensors go on mine last year and changed them myself. I didnt go back on the motorway until a few months after i changed them I took it carefully on the first trip as initally the light came on like before, but it soon went off. I think the sensor just needs a bit of time to "bed in" - (thats my view anyway). Haven't had any problems since the sensors were changed and have done a couple of 350+ mile motorway stints.

And yeap, I used the Big Jimny forum to find out what the problem was and how to fix it

Thanks for your reply Nelson.

I really hope is nothing bad and it's just a bogus alarm. But, maybe I'm being paranoic now, I think the engine is not running smoothly, round... I feel a bit of loss of power and some trepidation. Don't know exactly how to describe it. Use to drive a Renault Megane before and that one had some problem with the induction coils.
From time to time one of them asked to be changed, so I've changed like 3 out of 4. Jimny simptoms are a bit similar with what I've experienced with the Megane... loss of power, the engine not running smoothly... Wonder if it's the same problem?
Anyway, I will have it tested today and see what the problem code is. Ufff!!

UPDATE: went to the service and the reading was P0420 . The guy said this could mean anything and he cannot point to a single cause for this. So he cleaned the air intake as much as possible, advise me to use some CataClean (which I already bought and mixed with the fuel) and clear the warning light on my dashboard.
However I don't have much confidence that "this was it". Next time I will drive Jimny on the motorway who knows what will happen! Better take an off-road shortcut

OK, now I have officially broken down

Today I was coming back from work, at one pint I accelerated up to 3000 RPM in 3rd (or 4th) gear and the engine was behaving as if I hit some kind of rev-limit: starting to lose power from engine, like it was cut-off from the wheels (the rev indicator was steady but the revs were not increasing even if I was pushing the gas pedal)
Then it became worst, the same happened when at 2500 RPM, then I could hear misfires, then at 2000, more misfires (pac-pac-pac all the time), I could not reach more then 20mph, then 10 and then the car barely moved, vibrated badly if I tried to accelerate and... the end. I couldn't move at all, I was trying to stop the engine, wait a few minutes... but in the end I had to call the rescue truck.

I was waiting for the truck with the engine stopped, so it was a little bit better then: I could easily maneuver the car to get in position and put it on the truck. When I arrived home it was even better, no more vibrations, it was behaving normal at low speed (1st gear) making me think that if I could just leave the car for an hour or so probably I could have taken it slowly home. But when I push the gas pedal again it did the weird stuff (misfires, vibration)

Now I have to take it to the garage but those guys are not specialized in Jimnys... And a Suzuki garage will skin me.
I live in NW London, if you know a garage with some Jimny experience and is not too expensive, please shout!

To complete the story, since my last post the car still had some issues at high revs (I felt some slight loss of power, like "it didn't like" being revved, so I avoided as much as possible going over 3000RPMs. The problem was a bit more obvious when the road was going just a bit uphill and the car was at 40mph, in 4th or 5th gear at 2500RPMs, the power was suddenly gone, like the engine could no cop.

Then, for a week or so it started to be a little bit noisy at >2000RPM, it sounded like the exhaust was broken. So I was going to take it to the doctor anyway.

Anybody can share some light over this problem? I hope it's not too bad, otherwise is bye-bye Jimny. I really hope I can drive my Jimny again, I started to really like it. Ufff!

Is the catalyst blocked in the exhaust?
Sometimes they break up inside and cause a blockage further along the pipe too.

Don't have any idea about that...
Tomorrow I will take it to the garage and they will look (I keep my fingers cross the car will make it to the garage). The problem is it could be anything. I was reading on the forums yesterday and I found similar cases but there were different suggestions for what could trigger these loss of engine power... And there is no way to know for sure. This is probably what they will tell me tomorrow. I'm a bit depressed about this, I thought Jimny will be a strong car but it's proven to be exactly the opposite. Or maybe it's just bad luck.