Result? It sounds deeper, revs a little better, stops with firm-pedalled authority and goes round corners faster, with sharper steering and a flat, planted feel. Which may be what some owners will like, but the standard GT86's delightfully accessible progression from grip to drift has suffered.
It's almost too good, and part of a GT86's point has been lost. In this form it's simply a very precise, very grippy sports coupé, and if you do get it out of shape it gives you less time to think about sorting it out.
What's it like?
On, then, to the future 'enhanced' GT86, a version which as yet has no specific name. Here, the changed parts are to full factory standard rather than that of the high-end aftermarket, and are less extreme.
Again we have 18in wheels – these are BBS items – but while the rear Michelins are again 225/40, the fronts are 215/40. This is not specifically to alter the front/rear grip balance (although it does), but rather to conform to Toyota's factory standards for tyre-to-body clearance. Production cars will have bespoke Bridgestones or Dunlops.
Brakes and springs are standard, dampers are uprated Sachs items, and in place of the standard Torsen differential with a 4.1 final drive comes a mechanical clutch-type unit with a 4.3 ratio. A large rear wing dominates other aero enhancements, the whole package effective from just 30mph.
A different TRD exhaust fluffs and pops on gearshifts, while an extra door-latch mechanism jams the door solidly against its body aperture to boost the bodyshell's torsional stiffness – a feature which would no doubt be useful in any future open-top GT86.
This GT86 feels quite similar to the TRD car, the test track's dry surface showing up little difference in the differential's behaviour while the softer suspension lets you feel better what the GT86 is doing as you explore the wide tyres' grip.
The tail feels yet more nailed down than the TRD's but more trustworthy as it nibbles at the edge of grip. More of the standard car's character is retained here; you're just cornering more quickly.
Should I buy one?
The killer is the price: Tada reckons the changes should add just £800 to the build cost of a GT86, so if you think the standard GT86 is just too driftable on its Prius tyres, the answer is here.
Development continues with no launch date yet confirmed, but meanwhile Toyota GB will announce a standard-chassis, cosmetics-only TRD trim level early next year.
Whether or not a grippier GT86 is a good idea is debatable, of course. For my part I reached the highest test-track speed in the standard car, simply because it's so easy to drive on the limit.
Give it more grip, and you'll need more talent to have the same fun.
Toyota GT86 evolution
Price na; 0-62mph 7.4sec (est); Top speed 140mph (est); Economy 35mpg (est); CO2 190g/km (est); Kerb weight 1275kg; Engine Flat-4cyls, 1998cc, petrol; Power 197bhp at 7000rpm; Torque 151lb ft at 6400-6600rpm; Gearbox 6-spd manual