So, unfortunately the V1.5.5 update did break the sound for pretty much every mod. I have fixed it so you can hear those V8s roar again!
I was driving a few laps a couple of weeks ago, I noticed that the car felt quite strange. As it turns out, when I copied the Reiza physics to put in for these cars, I accidentally grabbed the Oval version, instead of the standard.
After fixing that I was having a thought: In 2003, there was only one compound of slick tyres and it was quite a hard compound (Drivers were doing more that 250km on one set in some races). To help simulate this, I've decided to put the tyres from the Stock Omega (1999) on these and I think they work great.
Lastly, someone requested to have the car liveries shown when selecting a car. This has now been implemented.