jaminescort1985

hey guys & girls, heres the story so far any help or advice would be really really helpful. i've put an rs1800 engine in my mark 6 escort and i'm having problems with it driving. it idles ok but when i drive it it has a massive flat spot from about 2k revs upwards. the only thing that i can think that it might be is that i'm using an air mass metre from a mark 6 escort gti, not from an rs1800 as they cost about £300 new and so far i'm having trouble finding a secondhand unit. if anybody has any idea why this is so and what i can do about it, you really help as at the moment i'm without a car.
thanks peeps
jamin