okay this all started a few weeks ago when it was extremely cold and i got full serve gas and the old fart put in regular gas.i was on my way to work(immedatly after i got the gas) when i noticed The car would hesitate, and woundt want to boost above 10psi (set at 14 on t25) but would only do this upon acceleration under 4000RPM once i got it above that the car would run like it always did. now i did leave the car outside in sub 0 weather for over 6hours. when i got off work the car would start but immedialty stall out withing a second. so i got it towed home and put it in the garage just figuring it was the bad gas and super cold weather.
In the morning i got it to start up but it was idaling very ruff and still acting just like before(and still is) also the check engine light came on immedalty.I got the code pulled and it was a misfire on cylinder #3. I clear it and it always comes back.

Now i relize this can be many things but i havent been around DSM's very long( only had the car 2months) and just wondering if there are any common problems that would give me ahint on where to start or any suggestion you guys have would BE HIGHLY APRECIATED as the nearest dealer is 4hours away and no body in my town will touch this car (never sold in canada) and out of 25 shops i called 23 lied to me and said that they could not even pull the code... and the one wanted 50 dollars finnaly found a place that would pull the code for me

my car is a 98 GS-T with very minimal mods (boost controler,intake,filter,bov)

thanks for you time and hope you guys can help me out