Take out the spark plugs & look at them. Compare against the pictures here on this link...

http://www.ngksparkplugs.com/techinf...q/faqread2.asp

You replaced the ECT sensor, otherwise I'd suspect that. Maybe the O2 sensor? How old it that?

I'm not sure but I think code 43 is kind of a catch-all code, when the ECM can't say any single sensor is obviously fried, but overall the system isn't right. For example if the ECT or O2 sensor is reading wrong, but it's not so bad that it isn't reading at all. The ECM can only blame a particular sensor if it's completely dead or unplugged.

Have you managed to get your hands on a Helm book for that car yet?