i got the plugs /coilpack 2 and fuel filter changed and man did it make a difference in acceleration and power! the mechanic went with a colder Beur Plug not the bosch 6 plug . But then i noticed when the car idles it will occasionally have an uneven puff sound in the exhaust and the cars idle speed will will drop for that split puff and car shakes a bit. no CEL or anything else. at speed car drives awesome full throttle no problems like before, has anyone had these issues before?

 

Ah, let's get some basic info here, please. What type of Prosche are you talking about?

 

sorry 996 TT

 

First, I assume that you and your mechanic have tried all the usual things, and that the car is serviced properly with everything checked by the book, etc., which your message seems to imply.
Two thoughts then. First, I'd suspectthe fuel for two reasons: a) my experience is sometimes the brand of gasoline makes the difference in problems like this, b) at this is the time of year many gasoline manufacturers slip a little bit of ethanol or other "winter" additives into their product for cleaner cold-weather burning. Lots of cars get a mild case of rough running on this. My 2004 (non-turbo) 996 really didn't like "winter gas" from my normal station -- it would run on the mixture but would start poorly, and just sort of randomly decide at times to run a bit rougher at low throttle, etc.
so, you could switch brands of gas and just try. Or more --In my neck of the woods (central NC) there is one station who sells 103 octance "racing gas" - ask around and try to find one near you that sells something similar. Usually 100+ octance gas is really expensive ($5.50/gal here) but a tank of that pretty much settles the point: if your car doesn't like 103 pure gas then its got some other issue. If you can't find this, pouring some octance booster into your gastank does something similar although I'm not sure how it mixes/acts with the winterizing additives in normal gas.
If this does not fix the problem, then my second thought would be, did you buy this car new? If not, it might have been modified/re-tuned during the time prior to your ownership, and have parts of the modified tuning still in its ECM memory -- after exhaustiing other options, having a good shop reflash the engine computer with the original stock map for your car might fix the problem. This can be expensive and requires finding a really good shop (or dealer) and so I would hold it for a last desperation measure when all else fails.

 

Clean your maf sensor.