Solved. Went to lexus and they told me it was normal for is350s.

Basically high pressure fuel injection using direct injectors.

You can hear a bit of a knocking sound after start up. I have experienced similar knocking sounds like that when spark plugs were not torqued to specs and/or the wrong oil weight was used. You should have checked out by a mechanic to make sure it is not something serious - good luck.

Honestly it sounds like any is350 engine. I could be wrong as i was listening to it on my cell phone.

Yes this is normal from what ive read around on the forums and have heard on my on experience. Its the direct injection it was makes the engines kinda loud from what the guys have said on the forums.