[Gary C]

the shocks *do* help, if you get something like a KYB adjustable .. if they have a fitment for the PT that is. Reason being is you can change the stiffness of the shocks, and thus dial the front suspension in a little bit firmer than stock, with the rear firmed up all the way to help prevent the squatting which unloads the front tires.
The other thing which doesn't *add* power, but helps it get to the ground better would be a set of uprated motor/trans mounts. Reason being it will help cut out the serious wheel hop issues, and instead turn that into a firmer mounted drivetrain with wheel spin vs wheel hop. I'm seriously afraid *even on the street* to launch fairly hard as I don't want to bust one of the stock mounts, untill my upgraded ones are here. You will get vibrations into the cabin though. As far is warranty is concerned I've never had any issues with prior cars, and some even had full solid mounts.