when i replaced the lower pipe with high flow part i was impressed with the loss of smoke but it did move power band up / less low end grunt . I think you will notice a positive difference, i had similar mods although i have a larger smic
Less than 10K on this motor/components. R520 7 holes popped by reputable vendor and given clean bill of health. Car was not nearly as fast as it should be for what was done. Pulled to head for other reasons and found this;
# 1&2. Nice, light covering of soot as normal.