The non-foulers were about $5 at autozone.
Anti-seize lubricant about $3.

The 1/2" hole was drilled by placing one of the non-fouler spacers in a vice and drilling with a hand drill. It is much easier and more easily centered by using a drill press. No matter what, besides a few dollars, it just takes time to remove o2 sensor, attach to both non foulers and insert back into the exhaust manifold. Non counting the drilling time, removal and re-installation with spacers took about 10 minutes of time.

I had to remove a heat shield from the exhaust manifold and the sensor was a tough nut to crack! With the anti-seize lubricant, everything was a breeze.

If you have a drill press, 1-5 minutes is all you need so this is a 15 minute project and about $6-7 cost + time. There is enough anti-seize lubricant to do a couple dozen of these projects.

I left the compressed stock washer on the base of the o2 sensor. I put on the modified non-fouler adapter without any new washer/gasket onto the o2 sensor. I added anti-seize lubricant to the o2 sensor threads..be careful not to get that stuff on the sensor probe. I then put the unmodified non-fouler spacer on the modified one with lubricant and also no gasket/washer. I DID use a gasket washer between the 2nd spacer and exhaust manifold and of course anti-seize lubricant on those threads going into the exhaust manifold.

I hooked up all the wires again and then drove around a bit just to make sure nothing funky immediately happened and didn't really expect anything to.

Some of the lubricant from exhaust heat smelled after I parked when I stopped. That will disappear over a bit of time. when I parked I disconnected the negative of the battery cable so the fuel computer reset. It will remain unhooked for about 4-6 hours until I reconnect it.

The current tank is at about 3/4 and I'll know at the end of this tank if there is a difference. I keep good records of MPG and I'll post my results if it did anything at all or not.

I used the old O2 sensor. A new one cost $40 but with the RXP, it causes almost everything to burn since it links all the hydrocarbon molecules together...causing more to burn as it absorbs infrared heat. so this sensor is in good shape and hardly had any carbon on it at all.