The answer seems to be available at
www.airfleets.net.
This shows qty 20 of the 330-343X, qty 4 of the 330-343E and qty 6 of the plain old vanilla 330-343.
The X versions are reg 9V-STA to 9V-STY. omitting STI, STJ, STP & STS
The E versions are 9V-SSB, 9V-SSE, 9V-SSG & 9V-SSH.
See here:
Singapore Airlines Fleet of A330 (Active) | Airfleets aviation
Kelvin