Dunno about sim card making the calls sound quiet, but I had a problem with my TP on day 1 where I couldn't send any SMS messages...
Error shown said that the message could not be sent because the SIM card was not valid. Went to Maxis, got the card replaced and SMS now works fine.

So SIM card can affect some things at least, but I'd doubt it would affect call volume.

I've also tweaked my TP with most of those mentioned on the first post, TouchFlo flies now whereas there used to be delays when sliding and opening apps.

Download PHM Regedit from here - http://forum.xda-developers.com/attachment...35&d=1080290397
You'll need to register to download but there is loads of good info on the forums for Diamond and Pro so its worth registering.

Regedit itself is like Windows Explorer so browse the tree, then select Values, then either add or change the values/keys as guided.

If you search the XDA forums, there is also a cab file that you can install called Diamond_TF3D_Config_Setup.cab which has most of the tweaks built in so need to manually edit - just tick a few boxes.

Settings - System - Device Information.
Firmware = ROM version

You should find all of the Malaysian models are fairly up to date with 1.90.707.4 WWE (08/23/08)

No sooner do you buy a phone than you hear of the next version coming out.

dailymobile.se/2008/09/10/htc-touch-hd-pictures/

So when will the Touch HD Pro come out?