I need to have knock sensors replaced. While the manifold is off, what are the best parts to replace? I have already purchased ignition coils and spark plugs and gasket seal. My model is a 2009 rx350.

 

#1 - have not heard of knock sensors going bad... what makes you believe yours are?
#2 - "What are the best parts to replace?" - no clue what you're asking. If you're asking about things to do while the top of the engine is apart it would be spark plugs, coil connectors, PCV valve, clean the injectors/replace the injector seals. While you're at it clean the throttle body as well as the MAF, check for any oil leaks potentially the valve cover gaskets. If you remove the valve covers and notice any suldge build-up run a pint of Seafoam in your crankcase oil for maybe 100 miles then drain adn refill your oil this shuold remove gunk and sludge
#3 - I hope you ordered OEM coils NOT aftermarket as they are known to be of suspect quality and the originals rarely fail so that begs the questions of why you might be replacing them
#4 - most OEM parts can be pruchased via the several Toyota/Lexus sponsors on this site for far less than dealer pricses

 

Honestly I wouldn't replace so many parts at one time.
I learned my lesson on this and it was painful. Lol

Adds a lot more steps to retrace if something goes wrong.

I would replace only things under the manifold and hold off on coils and plugs, and all other etc for another day.

One step at a time if you want to play it safe. 😁

 

I was planning on replacing the valve cover gaskets on my 2006 lexus rx400h but decided to postpone it and just do the front instead. The rear valve cover is under the intake manifold and it's better to replace the below while you're in there..
- pcv valve
- valve cover gasket
- ignition coils (if they are still original)
- spark plugs and hole seals
- knock sensors (if they're defective)

It's likely possible that the ignition coils connector plug clip will break (and that happened to me, all of the 3 in front) I guess heat makes the plastic plugs brittle over time. I have to finish the front, work on the rear later until I have the new connectors/plugs. I'll be replacing the brittle connectors/plugs when the weather gets warm.

 

Just had all this done on my 2004 RX2004... except the valve cover gaskets. That would have made sense. C'est la vie!