I can see your point about smaller lumps. It's true that a diesel engine, regardless of the torque or power on offer, is heavier than a petrol unit, which can compromise handling, especially in front wheel drive cars.
It's not just outright grip (which is very good on any Peugeot - it's been a family trait for decades) but you've still got the momentum of all that mass over the front 'axle'. For me, it's not a problem as my car never sees a track - it spends its miles on motorways and fast A roads where the re-mapped diesel's mid-range clout is invincible.
Try and extract 309 lbft from any non-turbo petrol this side of four litres and you'll have your work cut out. Manage it and you'll have a big overdraft and a job keeping the thing idling below 2000rpm
I've never set much store by 0-60 times but the 406 saloon I have manages a conservative 8 seconds. Flat out, no idea but it's pulling hard still at 130mph, although diesels don't like massive revs so that will compromise the result. Again, it's the mid range stuff that I think really counts. Try 40 to 70mph in fourth in about 7 seconds!!!
Good luck with you efforts.