I think the conversion is really impractical. I had a 1998 T5 (cable) and wanted a wagon so bad I found a 1999 V70 T5. I wish I had the 1998 cable. It took me awhile to resolve the throttle body issues on the wagon...and in an unusual twist...the cleaning worked. But it was not really a dirty TB, it was a plugged hole in the manifold, called a "banjo" hole.

I suspect this conversion would involve a new computer and you would have wiring harness issues. The TB you have has no provision for a "cable"...it's electronic. So now you are replacing the TB, probably the computer,...and who knows what else. If it could be done correctly, I realy don't think the emissions are an issue. But complicating matters further...1999's have a cylinder head different than any other year (according to the fairly sophisiticated parts interchangeabilty software in a local wrecking yard).

Now that I've got the kinks worked out of the 199 I bought...all is fine with the drive by wire system. That doesn't mean I wouldn't prefer a 1998 system, but to pay big bucks for something that might not work right. No.