Clive has hit most of the key points
You have to declare any changes even fitment of options from OPC, it does not necissarilly mean they will up your insurance but they want to know. The thing they were most interested in on the beast was the bodykit , even though it was a stndard porsche option fitted by a proche spcialist, that and the uprated springs and dampers - they wanted the specialist to reassure them the ride hight had not been lowered. As for the performance increase a tiny raise in premium (to ocver myself I ahd to ahve ti rated at 420bhp at Parr;s advice, it only went up in insurance over 400bhp)
DMS, Revo and most other remaps of any quality will re do your map if its overweritten. DMS and Revo are conservative and basically take advantage of the better european fuel so stay within porsche paramaters. Fpor all intents and purposes undetectable. However if there is an engien fialure and they investigate its atht hthat point they will look for a remap. So you have to own up. I did with my OPC and they weren't bothered. Revo also has a unit you can plug intot he car and reset the remap backt o stand ard fittings. It will also reset tot he remap and immobilise you car (ie turn the engien managment off until you plug in again). This is a good way of preserving your remap wihtout havignt o go back tot eh specialists after a service BUT YOU MUST DECLARE YOUR REAMP TO INSURANCE AND DEALER on or off.
Gains - are more drivability than in power. Which is good. on a DMS and Revo - they are a good and relatively cheap intro to remapping both are tacitly supported by the german parent Prosche GMBH so are unlikely to harm the car (not guanrentee mind). To drive you'll notice three things - 1) there were flatspots in the stnadard map that have mostly now been removed 2) If fells like your driivng witht he sharper throttle from sports m ode when its off, when the sport button is on the throttle is razor sharp and very repsosnive 3) because of 2 if you drive gain a more relaved fashion, eg motorways you might get lsightly higher mpg because the car is tuned tot he fule but once you flex your right foot it will be slighly worse (your driving harder).
The other consideration is "power" gaisn in top end power. this is a bit of a misdirection. The best maps get you more power lower down the rev range (so it does not add significantly to peak power) but remove flatspots and give a more responsive engne - this in turn makes a quicker road car than one when it all arrives in the last few hundred revs. The converse is true for race tracks where top end power matters more and speeds (therfore airflow to the engine) are higher.
So subtle increase at top end, general increase in performance all the way through the rev range and shaper throttle - better but not transformational.
There are other mods - exhausts and induction systems that if you put in make a significant difference tot eh cars perforamnce and character - especially with a custom remap doen on a rolling road. However this is a) getting costly and b) as I foudn out becoems too much for the standrad brakes and suspension components. Ian from Porscheshiop and myaelf designed a custom induction fro the gen 1 which was significnatly better thant he other options ont he amkret (I tred them all) and went with the reamp and miltek exhaust really well - Porsche cetnre driveer trainers loved the final incarnation of the beast car and always said it felt like it had come stright from the factory.
My C2S Powerkit ended up with 11bhp more than the Gen 1 GT3s at the treadblocks - ie before allowance for losses but weighed more - so the convestional suspension and brakes just werent good enough - at that point it got very expensive albeit had set a maximum budget and canged items whent the stadnard component wore out.
So if you must, try a well know remap like DMS or Revo but be aware it will acceelrate any problems the car already has but if you are sure its fine, you'll enjoy it but be warened its a dark slippery slope and once you start modifying tis hard to stop.........[8|][8|]
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