What is the purpose of rectangular port on V6 timing chain cover?

What is the purpose of this rectangular port on the V6 timing chain cover? It comes sealed with a cover and 4 bolts and it is on the right (passengers) side of the cover. Is it to enable optional accessories?

 

I re-examined and I think the cover goes right over the right side timing chain tensioner. So I think it is used to enable access to the tensioner to release the timing chain off the master camshaft sprockets

 

Bingo.

 

Optional charger port for a impulse quad flux cap.

 

That cover is known to rust.

https://www.tacomaworld.com/threads/rusty-timing-chain-cover-plate.334084

 

One of the advantages of the timing chain cover leak.........nothing rusting around it. Lol

 

Use it to adjust the chain???.

 

The chain's tension.

 

This owner has seen a lot of salty conditions. Look at all of the rust in the rest of the picture. Power steering bolt, power steering pulley's rod, shock tower, wiring harness bracket. Not to forget the corrosion visible all over the aluminum. That rust looks like barnicals.