2000 gt rough starts power in an out

well i have a 2000 gt with 66,000 mile on it . i just got this car 5 months ago and it semmed to be starting harder and harder when i first got my car al you could here was the zing of the starter. now it seems to shake alittle bit before it starts. ive replaced the fuel filter and put in a new pcv valve and air filter but it still seems to be a problem,also sometimes under mid to heavy accell it almost seems like my car seems like it doesnt have enough fuel and still wants to whine out. but when i floor it all the way it takes right off. i no this sounds funny but it seems like it wants to take right off .and some times irregular idle . i have taken the front three plugs out there ac platniums and look fine......does any body have any suggestions or should i just stop being a cheap ass and buy plugs and wires ...no modifications at present time on car