Volvo 240 DL, 1990 emissions

Hi, great site. Ok, I just purchased a 1990 Volvo 240 DL. Mileage 144,000. It's a 4 cylinder, it says on the sticker on the engine, also say 2.9 lbs. I don't get that, everything on the internet says 2.3 liters. Here is some info. I found:
Engine name: B234F
4 cylinders, 4 valves / cylinder
Turbo: no
Fuel type: gasoline, Fuel delivery: Bosch LH-Jetronic pulsed fuel injection
Displacement: 2.316 litres = 141.3 cu. In.
Compression ratio: 10.0 : 1
Notes: Double overhead cam (DOHC), low friction, tough and durable, interference head so make sure to change the timing belt every 50,000 miles! [URBANCIC], [GRIMSHAW1]
Cars that use this engine: (1989 740 GLE) (1990 740 GLE) (1991 940 GLE) (1992 940 GLE) (1993 940 GLE)

That should clear it up I hope for you knowledgeable mechanic guys. Ok, so now to the problem. I need this car to pass emissions here in Nashville, TN. It failed the hydrocarbon portion of the test. The ppm limit is 220 and my car had 343 ppm. I called a european auto repair place here and the guy told me to change the oil and run the car good and hot before taking it through the test again. I've had others suggest putting some 99% alcohol in the tank. My stepfather has suggested putting some fuel injector cleaner in it. He was also the one who said the oil had been changed recently, so that the suggestion of the oil change may not help.
The only discernable problem with the car is a rough sitting idle. The engine shakes quite a lot. But as soon as you rev it up it smoothes out. For some reason I feel this is directly related to the emissions problem. (But I know **** about cars which is why I'm writing you) :) The girl I bought it from said the engine never shook like that until after she had a tune up done several months ago, but I don't know how much stock to put in what she says. Oh, also my stepfather checked the timing and say it looks fine. He also fixed a little vaccum hose that was unattached. It looked like such a tiny thing, but maybe that coupled with changing the air filter (which he also did) will be enough to get it to pass. I just need some good advice, which, if any of the above suggestions should I take? And what suggestions do you have? I just hate the idea of paying big bucks to fix a car I bought for $200.
I did make a donation and I hope ya'll really do respond. A lot of the volvo questions had no responses. Thank you so much for any help. Have a great day.
Lorin