I see two Denso plugs for our cars. One is the Iridium TT that I use in my Fords, excellent plug(seems there is a single and three prong variety). Then there is another one for more than twice the price, looks almost identical!

DENSO 4705 Iridium TT Gap .040

DENSO 3473 {#3453, FK20HBR11} Iridium Long Life (SIP) - I believe this is what goes in the Toyota Box.

Both above are 3 prong.

I've seen some OEM single prong ones too, same part number.

 

you are right, 3473 is the OEM one. However, If i have to make a choice I will go with 4705, i think it is a newer part which has what they call twin tip technology. as you might expect, if there are no complaints then lexus wont switch to the newer part.

 

I'm running the Denso 4705 in my GS. Cheaper than the OEM and way cheaper than the NGK Iridium.

 

I'm convinced now any one is fine. I've seen oem ones on ebay without the two extra prongs.