Sealing ported enclosure to reduce boom

Is sealing ports and adding fill an option if you have ported cabinets that are boomy? Just got some Kappa 8.1 and bass is boomy and unrealistic. I like my Kappa 7 better which is sealed but the 8.1 has some interesting drivers.
Thanks, Mapman!

I use a modular port system in many of my designs, and on several occasions being able to ship a longer center section to a customer has saved the day.

The ability of the end user to make this sort of adjustment is a significant, and under-appreciated, advantage of ported enclosures over most other types. There is simply too much variation on boundary reinforcement from one room to another, as well as from one location to another within a room, for a successful "one size fits all" approach to bass tuning. Imho, of course.

I stuffed the port with polyfill. I guess if you completely cut off the airflow in the port the movement of the drivers will be compromised.
The ports are shaped like an "L" I think and are big (I can fit my hand inside). I don't know how I would be able to modify the port size without a lot of construction.
I haven't had this problem in this room (and in the same place) with other speakers (B&W, Polk, JBL, Infinity 7).
I had a pair of Dynaudio Focus 140s. They came with port plugs. I like the sound with them in better in my bedroom system. Just too much boominess without them. They sounded great with the ports plugged. And it was very easy to pull them in and out for experimentation though it was immediately clear to me that they were best left in for my setup.
"Sealing" the port is a bad idea. The drivers and crossover were designed to work with the port open, at least to some degree.
Knownothing, how would it affect the crossover?

Here's an example what you're effectively doing when a port is plugged.
Depends on the speaker, but if you have a three or more way speaker and multiple ported chambers, you could have some frequencies drop out if the mid woofer driver/crossover combo is "looking" to the port for bass reinforcement. Probably not common, but possible.