It's not too tight, I'd say little more than the old engine. I can't remember the figures, but the new lump is very close in weight to the old one, if not lighter. Old 12v lump is iron with metal inlet manifold etc, new 2.8 24v is aluminium with plastic inlet manifold. Car is driving really well as I've also replaced all of the brakes, refreshed the suspension, fitted new bushes, ball joints, drop links and bottom arms and a much quicker rack from a 330i Clubsport (E46 flavour)
Still doing a shakedown, but she goes considerably better than before. It's a very different driving experience though with the new engine being much revvier and delivering the power higher up the rev band. I now also definitely need to fit a LSD as the wheels spin in the first 3 gears!!