i have a 1970 bronco, last year installed a 92 5.8 truck motor and e.f.i. it runs great except it has a surging problem and it has gotten worse, only does it under a light load. i have checked fuel pressure while driving, tried different i.a.c. valves. made a manual iac valve it does not seem to change much, engine is mostly stock, except the heads were ported and a r.v. type camshaft. anybody have any good suggestions.