[gumba]

Can your cams be re-ground to 964 spec?
Elgin did my stock cams to their Turbo S grind. You'll need to have the rockers done, about $500
Turbocraft did the valve job, ported the heads, match port the aluminum injector blocks and intake manifold. Around $2500-3000.
If your having the heads done, it shouldn't be that expensive to add a second plug hole. Also not sure if needed if you stay with the 3.3
These are prices from a few years back, so best to confirm.
Also send the injectors out for clean & test
You may want to add the BLeask rpm switch
I used a Electromotive xdi controller which can be set up as single or dual plug.
Fun stuff.