Zool

hello chaps rite here i go, when i set off in first givin it some then change to second its as if the engine dies but doesnt if u get me. u could say it just looses power. ive only had the car two months ive got a back box and hks dump valve, i have noticed there is a slight blow from the back box which is on my to do list what do we think, im new to the site oh and my car is a uk 00 model any help or suggestions would be appreciated