Chevy Lumina 98 - 156,000 mi - 3100 V6 (automatic)

Car running hot, adding antifreeze every few days, saw water leaking @ W/P. Changed water pump & thermostat. Ran fine wk or 2, overheating again, saw water & oil mixing (w/ checked oil), bad intake gasket. Car stopped won't start. Chaged intake (manifold) gasket, head gaskets(heads not cracked or warped), oil & oil filter, and coolant. Egines noise, running rough, sounds like needs oil change still, drags a min. Before shifting gears & still running rough. Ran rough 2 days, changed shift module (f/ 95 or 96 lumina @ pull-a-part) ran little better little trouble shifting gears(engine noise) 4 days later running lot better, shifting gears better(little hesitation shifting & engine noise still) 7 days latter, idle high at start like accelarator stuck a little, drives like stuck in gear(idle high) driving or stop. Changed o2 sensors(both), spark plugs & wires, changed oil & oil filter again (notice oil was low & oil leak under car before change) also had gasket worn coming f/ tube connected to pcv valve( not the pcv) but the piece going into the top of the intake from the pcv. Made gasket w/ silicone water pump sealant. 2hrs. Start fine (idle much better) still little engine noise ( added qt. Lucas oil stabilizer @ oil change) also hasn't run hot since changing gaskets & stuff, but runnging as described. Drove after all the changes & no change still idle high (stopped & driving) still drags to shift gears ( up to 25-30mph, then again round 45-50mph) running & driving real rough (high idle, engine noise) sounds like a race car when you drive it. I'm really stumped, can you please help me?