I fitted the full Librands manifold and twin exhaust system to my 1991 +8. The difference in sound was awesome. My only criticism was it was a B****d to fit so I would definitely recommend you get a dealer that has experience in fitting the system to carryout the work.
Worthers
Seconded , a diy job will take you at least 2 full days of work and those around you will learn a lot of new words.
Do go for the newer type manifolds which exit through the chassis, the under sump crossover system is a b****** to keep leakproof.