First, a lack of low end power is what would be predicted from using a D cam in a carbed B18. Essentially too much duration and overlap for a carbed street engine
where low end and midrange are priorities. It being a B18 rather than a B20 makes it worse. ( If you ask which cam would be best I would tell you one of ours, since we developed them to solve these problems and still give good top end power. )

Second, for further tuning you need to determine whether the engine is now running rich or lean, and at which ends of the RPM range and throttle openings. There are probably 100 or more needle options. See the charts at http://www.rrocncr.org/technical/SUChart/SUChart.html
A quick way to tell which direction to go on the needles is to raise and lower them
in the seat. Measure the exact amount and raise in something like .050 or .100 increments. If the car runs better with the needles raised, then go to a richer needle on the chart. If it runs better with the needles lowered, then go to a leaner needle, or at least one leaner in the range you are trying to tune. If you find a good combination with the needle you have raised or lowered, you can match
the stations of the raised or lowered needles with one off the chart and make further adjustments to the low or high rpm range in he selection. You can also play with spring pressures to make the mixture leaner or richer.
The easiest way to do all of this is on a chassis dyno with a widebanc 02 sensor
for air/fuel ratio readings. On the dyno, with the air cleaners off, someone can also see what the amount of needle lift there is at the point where tuning is needed. This helps in choosing an alternative needle.

Joe Curto at http://www.geocities.com/jcurtoinc/ probably has the best selection of needles in the US. Tell him I referred you.

Very nice looking car!

John Parker
V-Performance.com