Ok. Just so you know, by porting, I mean actual porting of the plenum and not cleaning it. It won't be dirty unless the lack of the filter has made it that way. To port the plenum it needs to be ground out. There are guys that do this for about $80 or so and do a good job. This would be a great match with your larger TB that you have on the car and the spacer.
Place a post either at
www.mustangtuning.com or at modulardepot.com. You will find someone who does porting.
I assume you adjusted the idle by rasing the idle set screw right? To make sure the idle is set correctly, you can start the car and let her run. Then unplug the Idle Air Controller. It is located on the front of the upper plenum and has a hose running to it from the intake hose. The IAC allows air to bypass the TB when at idle.
With the IAC unplugged electrically, set the idle so that the car will almost die but does not. That is where the idle should be set. Then plug the wire harness back in. You should throw a code, but you can reset it by unplugging the battery.
Under Drive Pullies do not impact timing at all. Nor, do you need to change the timing with them. They are simply pullies that slowdown your AC and alternator etc... They will free up about 8 - 10 hp and they are safe to use. They require a little work to install, but they are not too bad.
To advance your timing, you have two options. A Timing Adjuster (TA) is aq mechanical way to advance the timing. You can safely advance the timing with a TA by about 3 - 4 degrees with 93 - 94 octane. You might get a bit more, with colder plugs.
Keep in mind, that the car's ECU changes the timing automatically across different rpms ranges, so it is not a linear setting. With the TA, the timing is bumped across the entire rpm band.
The second method is to use a chip or a programmer. There are mutiple options available out there. I use an SCT 4 Position chip with 3 custom tunes. Works great with my nitrous setup.