Hi everyone. I'm having problems about what to do to my 03 GT auto. I al'ready have a fender well cold air  intake and underdrive pulleys. I was wondering about how much HP you get from the TrickFlow intake manifold and plenium? or should I go with  pro products intake manifold, plenium, and 75mm throttle body. and if any anyone has one of these setups how do you like it. Also I was thinking about getting SLP long tube headers, catted x pipe, and a loud mouth II cat back exauhst. and last but not least does any one know what to do to my automatic transmision?And I plan to get it dyno tuned. any help is greatly appreciated.  

The biggest bang for the buck is to put a 3.73 or 4.10 in the car. I'm not sure if you drive on the highway alot, but if you do and you like to drive over 80 stick with the 3.73. This is the best thing you can do to get it to get up and go.  

thanks  

THe stock trannys suck you need to upgrade the input shaft and output shafts they break very easily I know from experience contact lentechautomatics.com for built trannys and parts your tranny is a 4R70W.tHEY ONLY HANDLE ABOUT 375 TO 400 HP RELIABLY.hOPE THIS HELPS