Misfiring and bad running

Hope someone can help, i have recently had a mi16 conversion into my 205 along with a set of Piper cams and for about the first week after picking it up all was great and then suddenly i started getting problems with it cutting out when standing or in slow moving traffic and misfiring when putting my foot down from a slow speed, i have been told i need a power boost valve as not enough fuel is getting through because i have had the cams fitted, could anyone tell me if this sounds right as Power boost valves are not particualy cheap and don't want to but one if it is not needed.
Also if that is the case then why was it not running right from the start?

A power boost valve might be the answer to your problems, try E-bay, you should be able to get a cheaper one there. I`d look at your distributer system/spark plugs first, check if anything is worn, also check your fuel pump and fuel filter, I just changed the fuel filter on my car and it made a huge difference. I`ve known a few people with Mi16 conversions and all of them have had problems.
Your fuel pump is under the back seats and is easy to check, just lift your seats up and listen for any abnormal noises. You might need a high flow unit to cope with the extra fuel needs for the Mi16, also the same with the fuel filter.