I have got a 4jx1 Holden Monterey 2000,and I have just changed the turbo,cause the other turbo blew last week,and since the change,the truck is smoking when you start it up,and when I get to a 100ks it stops smoking,but when I take my foot off the throttle,it starts smoking again,it also does that when idling

SOURCE: truck starts, dies. truck runs good some days,bad the next

I had the same problem with My 1990 F150 300 6cylinder 4x4.....I cahnged all the same things you did, finally I sprayed a can of Gumout through the throttle body and it worked and ran great. Now I add fuel injector cleaner to the gas and a regular clean with the gumout and the problem has'nt come back. Good Luck to you and hope it works!

SOURCE: my 03 wrx suddenly started blowing smoke

most likely the turbo, if its a darker or bluish smoke.

SOURCE: idle at 1500 to 2000 rpm

Most likely the throttle body gasket (between the throttle body and the intake manifold) is leaking.

SOURCE: Idle jumping up and down

MAKE SURE WHEN YOU PLUGGED THE SPARK PLUGS IN THAT YOU GOT THEM IN THE RIGHT FIREING ORDER,ALSO MAKE SURE THAT YOUR THROTTLE BODY IS OPERATING NORMALY WATCH IT WHILE THE CAR IS RUNNING TRY MOVING THE THROTTLE BODY ROD BY HAND

SOURCE: 2000 Avalon won't start and idle. Only while foot is on the gas

Avalons are prone to the the throttle body and Idle control valve getting gunked up over time. I took mine off, spent about 45 minutes cleaning it well with carb cleaner and q tips, and reinstalled. I haven't had the problem since. It is relatively easy, the hard part is not stripping the screws. Everthing is righ on top of the engine, not a hard repair. Mine did not have the smoke issue, however, it would start but would die as soon as you let off the gas.