I swapped from a d15 non vtec to a d16 vtec, the manifold went from 4-1-1 to 4-2-1 but I'm using the 4-1 manifold right now because I don't have a down pipe for the 4-2. How much does this effect my performance? the d16 is running at about 160-170 compression (108k on d16,) and it just seems no better than the d15 non vtec I just had in.. and driving it on the highway I could not pass 170 km/h with my foot completely to the floor for a good 5 minutes.. I could get to 220+ km/h with the d15... and it had 350,000 clicks on it and horrible compression. I'm getting a Header soon but I was just curious if this is my main problem right now performance wise. Thanks.. sorry if covered already.