I went from 243rwhp/296ftlbs with these mods(1.7rr, pulleys, headers, exhaust, cobra intake manifold, C&L Maf, stock TB, stock heads, stock cam. Then when i added my performer heads i dynoed at 287rwhp/ 310ftlbs on the same dyno. The #'s are all STD corrected. Theres about a 10hp difference...