Its both the ignition and the pipes that cause the problem, put pipes on first and it will be held back by the ignition, advance ignition first and it will be held back by the pipes.

Mine made 5bhp more just from the fywheel change, but it already had the JHA pipes fitted. I dont think that the tyga pipes would gain 12bhp on an MC28 if the ignition had not already been advanced as the bike feels like it hits a wall and doesnt produce any power that high up in the rev range.