liam get an interchangable decat thats what i had but i must say i didnt have any middle box and when i had the decat in the power gain wasnt noticable till high end power ... the interchangable decat/cat was mint though i was always swapping it took like 10 mins to chage over! only cost £60. also try www.mijperformance.com they do all my work and aint too far from you!