Gm has a bulletin in regards XXXXX XXXXX problem and it has to do with carbon on the valves and the valves not closing properly and not making compression like it should. Being you are saying it is turning over faster I would have to say that it sounds like it is exactly the problem you are suffering from. Here is the info I have on this particular problem. Let me know if there is anything further I can help you with!
Crank no start when cold. The engine may crank over very fast, as if there is low/no compression. It may also run rough for up to 5 minutes after starting the engine and may exhibit a P0300 DTC too. This may be caused by sticking valves due to fuel contamination. When the engine is cold, the compression on multiple cylinders may be at 0 PSI. The engine also may pop through the intake or exhaust while cranking and the spark plugs may be fuel fouled when inspected. Some engines may also experience valve damage or cam followers that are out of position as a result of this.
This condition will normally occur in specific areas of the country for a period of time and then it will no longer occur after the suspect fuel source has been consumed in that area of the country.
If the SI Diagnosis lead to a compression loss due to sticking valves, the following information may help:
If there is no sign of valve damage or cam followers that are out of place, perform the following procedure to free up sticking valves and to prevent the valves from sticking again. If valve damage is present or if there are cam followers that are out of place, perform engine mechanical repairs as necessary to correct the concern and then perform the procedure below to prevent the valves from sticking again.
Note: If the condition is not eliminated chemically, it may be necessary to remove the valves to manually clean the stems.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.