rocket#1

Hi gentlemen, This is my first posting, don't even know if I am in the right place. I have a big question that I need some help with. I have owned a 98 boxster for a number of years ,have built the 2.5 engine to about 277 hp. I have grown up with old school hot rods, this porsche stuff is a bit different, but I love it. I have been shopping for a 3.4 engine but fined better deals on 3.6 996 and 997's.I know the ECM's programs have been up dated, and many systems need to be also, but just how hard is it to up date these systems and how much extra cost in doing so? I would appreciate some council from one who knows.
Thanks rocket#1 p.s. my email is whirlwindtwo@gail.com