....and check the throttle linkage to make sure it is opening fully. On my 300D the nylon bushing in the firewall was wasted and even with my foot on the floor I was only getting about 1/2 throttle opening. Just a thought.

Though I would change the fuel filters as a general precaution. As a aside, has anyone noticed how fuel filters tend to get plugged up sooner these days? I remember going 30k between fuel filter changes twenty years ago. Today it seems that I have to change them once a year.