OK lesson learned, silicone not the best fix. Running it with the "patch" over the EGR intake tube, it still had surging idle when stopped in gear. Ran/drove fine besides that. Did another pressure test, found my silicone job to be leaking a bit, so got a new oring for that. Had to take out the intake plenum and carefully work the EGR tube to not bend anything. I disconnected the supply tube to allow a little more give. Oring seals on the plenum looked fine, cleaned both surfaces anyhow, intake gasket looked fine. Also rinsed out the EGR valve from the top down, opening the valve every few sprays to clean out the gunk. Cleaned MAF with MAF cleaner, cleaned dirty connections/grounds for coil pack as well, boots and wires seem to be fine.
Is the EGR valve supposed to "hold" a steady vacuum? My gauge is a little notchy, but it seems I could get it about halfway around the gauge tops, pressure would steadily (slowly) drop. Even used my mouth on it, definetley bleeds off pressure, but the valve does open/close.
Before I replaced the Oring, I got P0300 pd
, seems to be random/multiple cylinder misfire. Oh and also got 0113 from unplugging the MAF for a few seconds, which (while surging) ran better for about 2 seconds, then conked out. After replacing oring and checking all other vacuum connections possible, didn't clear codes and the 0300 went away, but it still surges at idle when in drive. Evap and Catalyst were the only tests not ready after about 30min of nonstop driving. So the 0402, 0171 and 0174 seem to be gone, for now.
I'm kind of at a stall, what else to look for? I'll give it one more day of playing around, but without a proper scan tool I don't want to throw any unnecessary parts at it. To review, it had 4 codes: 0402, 0171, 0174, and 0305. Cleared all those, repaired EGR tube, got p0300. Repaired Oring on EGR intake tube and all listed above, no more codes. Still have surging idle, maybe a bit worse now that I fixed the oring, but runs and drives excellent besides that. Also a little hesitant to start, sometimes, seems to be when slightly warm.
Sorry for a long post, but thanks to those who have read/helped. Its appreciated!