I've owned my 244 Volvo for over 16 years and over 200K miles later, and just last year I *finally* had to replace the head gasket because of a water leak. While I was in there, I decided to have the head cleaned up and the valves adjusted. The head was resurfaced, but I don't believe that they shaved off anything off the bottom of it. I got everything put back together, put on a new fuel pump since the other one was dead, and got new fuel injectors because the spray patern for the original ones was getting pretty bad. The timing is adjusted to what my shop manual recommends, and I have new spark plugs, wires, rotor and cap (all Bosch).

After all these years, I have never had to put in anything higher than 87 octane gas in my car until now. If I use the low-grade gas now, I get an extreamely bad pinging problem with almost no power. Not to mention that fuel economy goes through the floor. If I use the mid-grade gas, the pinging is dramatically reduced such that I hardly ever hear it.

My question is, why now? What can cause a pinging problem like this such that I have to now use a higher grade of gas? Is there any kind of adjustment that I can make to correct this problem or am I going to have to continue to pay through the nose for a higher grade of gas now? Is there a timing adjustment, sparkplug type, or specific cap and rotor model that I should be using?

The engine has over 360,000 mile on it total. Any suggestions you might have would be greatly appreciated. This weekend my baby gets sport load spings, Bilstien shocks, 25mm sway bars, over and under chasis braces, and a tower brace. She's gonna rock (well, actually she won't rock after this, but you know what I mean ;o] )!