another vote for the Permatune. i had one in my 85 Jalpa, and i was spoiled by it. along with Mike's excellent advice i would respectfully suggest you make sure that you have proper fuel pressure, a clean filter, and clean fuel lines in good condition. it could be the demand from the carbs is more than the pump can supply if its old or defective.. float levels are important too, but when in doubt, i would rebuild the carbs as Mike says and sync them. Pierce Manifolds in California has everything you need for the carbs.

Michael