What's wrong with V6 apart from power?!
The 2.8 Cologne had siamesed exhaust ports - i.e. instead of each of the six cylinders having one port leading into one runner on the manifold, one cylinder on each head had its own port while the other two on that had were merged into one at the head; leading into one manifold runner.
The result is that the cylinders with siamesed ports have less flow area and it cocks up the exhaust pulse phasing / scavanging. While typically large(ish) displacement multi-cylinder engines are tuned / known for a reasonable amount of torque at relatively low engine speeds, due to the cack head design the 2.8 doesn't get peak torque until quite high up (about 4.5k rev/min IIRC as opposed to the 3-3.5k you'd typically expect).
It also tends to make less than its headline output of 160bhp - IIRC back in the day a good one would make 145bhp on the rollers.. which is pretty pitiful when you consider the sort of specific output some of the Vauxhall and Jap engines were managing..
In practice you'd get similar revvy characteristics / power delivery to a smaller, higher-tuned engine, but with all the downsides of a large-displacement, heavy V6.