I need a company fairly local to London/middx to fit my supplied green 803s, supply and fit a 3 bar map sensor & matching chip then set it all up. any ideas on what it should cost and who is worth using? my car is a 1989 G 2WD

ps, what bhp should i expect to see, i have a 3 inch exhaust/bd10 cams/Cone filter....engine in great condition.