When installing your new Injectors, you need to make sure the seat at the bottom of the Injector hole is clean and level.
Then place the Copper Washer into the hole, and Injector.
You need the seat clean and level to insure a tight seal so you do not get compression blow by past the Washer.
Do a search for this Rotunda tool, T 83 T 9527 a 303 232.
They come up on E-Bay now and then.
Here is the cheapest one right now. $123.18
I paid less than $100 for mine, and was never used.
Goat