the gain was really noticable, the car feels free if that makes sence, it takes the entire rev range with alot less struggle, goes alot faster, its easy to do, i learnd everything about doing it from talking on here, i have no mechanical knowlede before that so if i can do it anyone can, there was something about that timing, i think the flywheel has to be 6 degrees BTDC, but itll still run fine if you just line up the timing marks, just need a timing light to finish it i think but i got a garage to do that as i aint got a clue, but as for the head its just nuts and bolts at the end of the day, from personal experience i advice not to seporate the downpipe from the exhaust manifold as when i put it back i never found a way to keep it sealed without it blowing even with new seal ring, clips and sealant, its really silly the way its done