Vibration when accelerating at +-2k RPM???

Hi,
I have a 2000 Jimny 4X4 with the M13A engine and the manual 5-speed transmission, the engine has had a cylinder rebuily I believe because my old grandma drove it without any oil and destroyed it, but that was years ago. The car has 148k km on it and 2k km ago i had the car serviced and they told me i should check the brakes and the steering joints. As all offroaders do, the steering wheel wobbles a bit between 60 and 80 kph, but that's a minor problem.
The main problem i wanted to ask you guys about is the vibration that i feel when accelerating in every gear apart from 1st. It only happens between 1500 and 2250 RPMs more or less, and it's stronger the deeper i press on the gas pedal, i obviously press it very lightly if i find myself in that situation and wait for the rpms to slowly climb before pushing more. Apart from that the car seems perfect, it also doesn't have any problem revving to redline and accelerating.
Any idea why it does that? I contacted some mechanic friends and they said it's normal.
Thanks in advance!

It's not normal, but could be anything.
Engine or gearbox mounts ok?
Just a starter suggestion, but it may be a problem that's best ignored.  
 

I don't know actually, i could have them checked just to see if that's the problem, but it isn't that serious. It still annoys me a lot tho XD