My late 97 (facelift) has been sluggish and sometimes backfires when I move off - it's OK when running. A mechanic recommended using fuel additive, this slightly helped but I reckon a new throttle body is needed !.

I have the chance of one from a 96 at only £30 UK - will it fit my late 97

I plan to fit it myself is it straightforward ?, I fitted a new throttle body to my Jaguar a few years ago.

Backfire when you accelerate might be from running lean. In the old carb days, there was an accelerator pump that momentarily richened the mixture when you accelerate. That's been replaced with a TPS that tells the PCM that you are accelerating. Before you rip off the entire throttle body, I'd try testing the TPS to see if it's in spec. Unless there is clearly a problem with the TB..