You're most likely correct about the Rev kit, I'm sure they did something.
On the 3-2 downshift, the 3/4 clutches disengage & the 2/4 Band, Forward & Overrun clutches are engaged. Engine/Compression braking is done by the Overrun clutches.
You can do a pressure check to get an idea of the Pump's condition, it may be fine.
I recommend the Alto Carbon 2/4 Band if you upgrade.
Is the 2nd gear crash/bang on the 1-2 upshift?
May be orifice in Sep. Plate too large or Accumulator problem.
I have a Billet Servo, can't remember if it's 2nd & 4th servos or just 1 servo. I got with some other parts I bought a while back. I'll send you a PM if I can find it, I honestly don't remember what I did with it.