Surging is probably something else. You will have to replace the chain and related
components to take out excessive slack. The valve timing can be adjusted by
selecting one of three locations on the cam chain sprocket.

 

surging can be caused by timing being to advanced, tps being out of adjustment, egr valve leaking or a vacumn leak.

 

I'd go for the egr valve being leaky or activated at the wrong time, i.e. egr control for the surging problem. Timing chain; well, hate to say it but if the cam timing is too retarded or chain has too much slack...replace with complete kit!! If you don't... it can get very expensive. All depends on how many miles on the motor though.