i am havin the same problems with my 04 gtp 3 and 4 are low on compression, and missfiring had full tune up done, put new injector in, switched plugs and wires all good. But still misses and low on compression. Aleak down was suggested by the mechanic, but if it could still be a bunch of other things not sure. I was told need new engine, bc possible valve job, or worse, and all that is more than a new engine. But if you had a valve job done and still have the prob, now not sure what to do either??
