Car makes noise at 2500rpm – Mitsubishi Outlander 2.4l mevic 2004

Good Day,.

After suffering a lot by different garages with empty wallet in the end decided to ask some help online, hoping maybe someone will help me,.

Car runs too nice and smooth below or above 2500rpm,

Mitsubishi Grandis 2004, 2.4l benzine, (sorry for outlander in car model, as no grandis was in list) Kind of rattle noise at 2500RPM at idle in neutral and when driving, 7 times to the garage, they replaced one by one , Engine mounts, transmission mounts,  drive shafts, Muffler, middle damper, and yesterday they asked me to replace catalytic converter, as they said its broken from inside, Pfff, no engine light, no error code on scanner, emission test passed, yet they insisted, i decided to check it 1st before buying one for 700 euro, or 450 for used one,

After disassembly, both catalytic converters at front with the manifold and one at the middle all were in one piece, not broken, not clogged, not lose. Leak or anything, heatshields were tight, even made them again in place with washers, were touching nothing,  so mounted back to the car, after that i asked the mechanic what now, and he said maybe its this and that so i came to conclusion that he just don’t know,

Now the question is,. what is causing this noise and that vibration in cabin.,. To describe the noise, its like if someone ever overfilled their engine oil…? kind of boooon rattle, i have this car since last year and this sound was there but a stupid friend said its normal for this 2,4 engine, after driving another grandis 2004, i know now my car has a problem,

any idea…? where to look for,. i have paid around 600 on engine mounts, 280 for drive shafts, and around 570 in total to that mechanic all for replacing parts which were not even faulty,. thanks God i didn’t bought new catalytic converter,

Please help.

Thanks

Brand: Mitsubishi
Model: Outlander
Year: 2004
Engine: 2.4l mevic