Will adding tungsten powder to change swing weight change feel of club or balance of head?

I have some KZG Evolution irons that are too light for me they are a D0 swing weight. My local clubfitter thought I should go with a D4. The shafts are Rifle 6.0 and I always liked the feel of thes clubs very smooth but good ball feel. I also have a set of FG-17 Wilson Staff blades that I wanted to freshen up and use more. So  we took a KZG 6 iron and added tungsten powder to the tip and by the way  I'm tall so I also had him make the club 3/4" longer so now it's a D4. The Wilson 6 iron head was reshafted with a FST 115 pro shaft. They are already a heavier head so they are around D7.
I took the two clubs to the range and now the KZG seems to feel heavy and dead. The feel of the ball on the face is kind of a "thud" they had better feel before I did this.

It seems to feel heavier than the Staff iron.
The Staff blades are much better I can feel the ball much better on the face and even though they are a heavier swing weight thay feel easier to swing. Seems like I can turn my hands over easier.
My question is could the tungsten powder have anything to do with this?
Would the powder absorb vibration and reduce feel? Would it change the balance of the head making it harder to turn over?
They have the same grips right now so maybe I could put Winn light grips on the KZGs and not do the powder and something heavier on the Wilsons? I haven't played with the Wilsons for many years and maybe it's just that cavity backs will not feel as good as blades.
Thanks for any advise.

Feel is an illusion, 90% of what people refer to as feel is just sound and unless you absolutely cant get used to the new sound it wont change the performance of the club very much.

I can feel it if I hit off the toe or if I hit it too close to the shaft and I can definitely feel it when I hit one dead center. Sound has nothing to do with it for me as far as irons go. They don't make that much of a sound anyway not like a Driver that's the only time I pay any attention to the sound..

You don't think of it as sound that's why you call it feel but if you put on some ear protection and took a few swings with different clubs I think you'd be mighty surprised at how little difference in feedback through the shaft there is from club to club.