Joe;

Does the engine have flat spots in the acceleration (Carb jetting?) or seem down on power in all operating ranges?

...generally speaking, the B18s had enough power to provide a good lever of performance (including easily keeping up in traffic nowadays)...when everything is tuned and working as it should! This includes breathing on the intake (air filter big enough or clogged?) and exhaust sides (4-2-1 is nice to have as BG suggests, but not the world...rest of exhaust system can stand to be opened up to 2"), and IGN (initial timing ⎜-18D BTDC]plus Cent. Advance is important as George has mentioned...without it, engine will feel doggy and like its up against a wall...I'd certainly pop the dist cap off and check CA quick, or with a timing strode if available). See also: http://sw-em.com/Volvo%20Ignition%20from%20Scratch.htm#Detailed%20CA%20Servicing

Cheers