adjustable pulse relay trigger

 Looking for advice on building an adjustable pulse trigger for a relay operating a 180 watt fuel injection line heater in a 2003 VW Golf diesel in a vegie oil conversion. Off the shelf units do not have the BTU or control I desire. Thermostat responce time is too large to keep the fuel line in the 190 - 220*F range.  Something like 20% increments would be fine as in 20 pulses per second, 30 pulses, ... full on.

What off the shelf relay will handle the amount of cycles needed for 50 hours operation per year x several years? I believe the relays I'm currently using have a 10K cycle life. Current system cycles in a 60 degree range.

My goal is constant temperature. I do not want the heat the fuel before past 80*F before the injection pump like many kits do.

Advice?

Also look in to solid state relays - quick switching and no contacts to wear out.  Solid State relays are used frequently in heating applications.