SlackAttack

Newbie here that could use some help: How can I determine if the vacuum leak that I have is from the upper or lower Intake Manifold. I am going to start on it tomorrow and I know how to test the and spider injectors when I get in there, but I don't want to have to dig down to the lower intake if I don't have to. I have a very high idle and a multi misfire code. Plugs, wires, distributor, rotor all good. Compression good, within 8.5% of each other. Fuel pressure normal, but it doesn't hold after you turn the key off. Recently tested or replaced and tested: IAC, TPS, MAP, MAF, EGR, http://shop.advanceautoparts.com/web/PartSearchCmd?storeId=10151&searchTerm=coolant+temperature+sensor and PCV. I sprayed an entire can of starter fluid on the entire engine and every vacuum line and only got a slight hit on the front passenger corner of the upper intake. Brake booster tested OK and when I pinched the hose did not change high idle. I have a pretty good OBDII reader and the live data, advanced DTC and ABS DTC was all normal, except for the multi misfire that constantly sets. I have checked all the moving parts on the throttle and cleaned them all, including the internal IAC passage. There is no wear or binding and the throttle closes tightly. I did a test that someone online said would show an intake leak: Block air intake from passenger valve cover, pull PCV and block hole, then spray starter fluid in oil fill. I got a slight http://rover.ebay.com/rover/1/711-53200-19255-0/1?toolid=10029&campid=CAMPAIGNID&customid=CUSTOMID&catId=6000&type=2&ext=112560277526&item=112560277526 from this, but not definitive. Also, the oil is clear, coolant doesn't have oil froth or bubbles, it's not burning coolant, no liquid or sweet smell at exhaust. Add in equal compression and I am pretty sure that the head is OK. As for the vacuum leak, I am about 99% sure that this is intake manifold, how can I:
1. Test before dissambly to see if it's upper or lower intake? Or both?
2. Test after I get the upper intake off (while I am testing the Spider and Fuel Pressure Regulator?)
Thanks in advance!
We love our suburban. we bought her with 60K. She is now at 284K and was still going strong... until just recently.

The Chevro

To be completely honest, if you're going to be pulling everything apart your best bet is to spend the few $ on new gaskets and just do them. Once the spider is off and fuel lines are disconnected all thats left is bolts and nuts and hoses. I just did mine a few months ago for the same reason and shes been badazz ever since. I upgraded to the replacement Delco fuel spider and the freshly cleaned intake just brought my truck back from the dead. 330k miles will give you some issues, lol. Believe me......take the extra time and throw the new gaskets in there. Plus once you pull it.......its gonna be DIRTY!!!! and I mean fugly due to the EGR. I soaked mine for a day and scrubbed the HeII out of it. Just that little extra peace of mind. Plus my EGR holes were plugged completely up. Zero flow. Just my 2¢

SlackAttack

I think you are right. I am just going to do it. It doesn't cost much and I can test everything and clean everything once I get in there! Thanks! g