If the injector was indeed bad it was a fluke. The ticking noise may be a valve lifter which is common with these engines and not a big deal. My advice is to get your car out of that shop ASAP or you're going to make someone's boat payment. (If you're still under warranty this should be covered by the way.)

Rough running and check engine light are classic symptoms of a vacumn leak which is a well documented problem and VERY easy and CHEAP fix. Ask your Volvo tech to investigate.

For the full story on vacumn leaks in our 850s, go to:

http://www.volvospeed.com/Repair/vacuum_lines.htm

You don't mention if you're mechanically inclined or not but sounds like you're familiar with the basics. Think about it. If there were too much raw gas in the cylinder, the valves would be closed (or very near) when the piston came up to compress the mixture. What would likely happen in this scenario would be a bent connecting rod. (Don't even mention the bent rod idea to the shop, why give them a more expensive idea.)

If I were you, I'd find an independent Volvo shop and get a second opinion. Either way, warranty or not, don't let them pull your cylinder head and go after the "bent valve." Check the easy stuff first.
--
Erwin in Memphis, '95 855t