I have a 5.7 liter. I am having problems with the engine missing at a certain rpm. Just before shifting to next gear it will start missing. And also misses in between acceleration and deceleration level. When I mess around with the vacuum it straightens out for about 20 miles and goes back to square one. Hope you can help.
Check to see if the gasket below the tbi unit is leaking. Spray choke cleaner there and if rpm changes you found the problem. They have a habit of breaking under the tbi. Also check your pcv and map sensor hoses as they get soft and suck together. You might try scanning for codes as well, you can go to trouble codes on site here andlook under obd1