uh to be honest how can your feel your intake filter is restrictive...
according to AEM they make the highest flow filter but i hear that the HKS is good too. the problem with the HKS that its a purely foam filter and it may not filter particles as well as a proper filter.
i say drop some money for the AEM instead. the HKS is way too expensive and its not worth it unless you have a turbo and it requires massive airflow