After test driving a 2006 GS300 ( I currently own a 2001 GS300 ) I noticed a slight 'ticking' sound from the engine. Most notably from under the car.

The mechanic tried to sell me that it was from the fuel injector, that it is larger because they added horsepower and therefore made this noise.

Doesn't sound reasonable to me.

Also, I didn't see any navigation feature on the in-dash screen. Is the nav functionality something that can be added?

Thanks for any help/advice.

he could be right. the direct injection system makes a ticking noise that you don't hear in cars without it. it's not very loud but it does sound like ticking.

All the 3GS makes the ticking noise, some much louder than others. If the noise in the car you look at bothers you, then look for another GS, because the noise cannot be fix.
The Nav will be very expensive to add, you need to change the center console, nav screen and add all the electronics and voice command.

Agreed, if the noise really bothers you and you really want nav, find another GS. I don't think it makes sense to add the nav after the fact (which, as The G Man said, requires you to change the whole console).

Ticking noise? Get out of the car immediately and run like heck, it could be a bomb!

The timing chain can make some noise too. Listen to the noise at a cold start, if its the valves or the lifters making the noise, it will be louder when the engine is cold.

Ending up buying a different 2006 GS300. 52,000 KM.

Dark grey on black.

Beautiful car.

Now will do the Nav/Bluetooth mod, get some sort of MP3 player gizmo.

Thanks for all of the responses.

(I think I twisted my ankle running from that car with the ticking noise)

It sounded to me like the Nav screen just wasn't navigating, but that it already had the Nav installed. The dealer/car lot it was at probably took the Nav disc out of the drive (in the glove box); they often do that at dealers, as well as removing shift knobs to prevent the vehicle from being stolen.