09 FLHR, Monster Ovals. Proper dyno probe insertion ?

Potato Man

Current setup: 09 FLHR, Monster Ovals, PCV with Map22, K&N Intake Kit

Hello Folks.

I have an issue regarding the proper dyno A/F probe insertion with my Monster Ovals. Here's the skinny.
I put my ride on a local dyno that is brand new to them. So they are not all that experienced. A few runs tuning the PCV revealed a lean condition above 3500rpm that required adding fuel. A lot of fuel IMO. I left the place with a reasonable A/F curve; but still high and shaky (14-15 from 3500-5500). Here are the power results.

Stock
HP= 63.2
TQ= 73.4

After Monster Ovals, PCV with Map22, K&N Intake, and dyno tuning
HP= 72.8
TQ= 84.4

Not too bad here. Although I thought I would gain more.
I think that the A/F being lean may be due to improper probe insertion in the Monster Ovals. There is a solid baffle about 4 inches from the end. The probe was secured at an angle to get in contact with exhaust gases coming from the perimeter baffle material. This doesn't seem right IMO. Four inches of insertion doesn't seem enough. I have read that the A/F probe should be inserted as deep as possible; the deeper the better. If this is true then maybe my lean condition was a false reading due to the poorly placed A/F probe, and we tuned in more fuel unneccessarily.

Any ideas on this theory?
I have also read about drilling out baffle plates to allow for proper probe insertion , and then installing plugs in the holes after. Is this a good idea ?

Regards