1993 Suburban Engine Additive Question/Shudder

[1993Suburban]

Once again i apologize for my many posts about this vehicle. 1993 Suburban 5.7 350 engine, automatic transmission, 4X4, 152,000 miles. Maintenance hase been kept on the up and up by me and the previous ownder. This question regards engine additive and slight shudder. The shudder occurs while taking off, and while letting off the gas pedal after traveling at a maintained speed. I notice also a slight shudder while maintaining 35-45 MPH, and then while letting off the gas. Also is pretty obvious while letting off the gas at highway speeds. I have owned the vehicle for 1.5 years and have always noticed it, never getting worse, however recently i read about sea-foam and it's amazing ability to gain back engine performance. About a week ago i picked a can up from Checker Auto Parts, and i followed the directions on can. I put half a can into my gas tank, and the other half was sucked through the brake booster vacuum tube. The usual occured (usual according to users of sea-foam). The engine acted like it was going to stall, so i kept a small amout flowing into the tube, when i neared the end of the amount i was going to put in, i tipped the bottle all the way up, pouring the rest in and stalling the engine. Let it sit for about 15 minutes. Started it up, smoke screen out of the tail pipe for about 10 minutes. Took it out on the freeway, and WOW! Durastic noticable difference in power, and idle speeds. My Suburban acts almost like it was rolled off the assembly line. Also the shudder I previously mention was virtually gone, only noticing it while letting off the gas at high speeds. I absolutely can not feel it anymore while taking off, and while letting off the gas at speeds lower than about highway (60-75 MPH). And even while i feel it when letting off gas at high speeds, it occurs much less and less severe. Would another half can of this stuff in the vaccum tube be a bad idea?
Maybe half in vacuum tube, other half in crankcase? I apologize for the novel, however i would appreciate any suggestions or info from someone who uses this stuff. Thank you again.

~Suburban Freak~