any problems with cylinders or rocker arms engine problems

Dear lanmankc-- There are plenty of technical service bulletins that have been issued regarding the 2004 GMS Envoy, but that doesn't mean that real chronic problems exist. It just means that the manufacturer has taken steps to handle commonly recurring problems with the vehicles they have built and sold, short of a recall notice. Our government has a site that posts these bulletins and you can have a look for yourself regarding your Envoy. Go to-- http://www-odi.nhtsa.dot.gov/cars/problems/tsb/results.cfm. Good luck from Bovan.