My 96 Olds 88 is having problems with fuel milage and coolant disappearing. At first i think it could be the same problems most have with the UIM plenum leaking from the EGR. It hesitates under load, can not accelerate hard but it can get up to highway speeds without hesitation and stays there if acceleration is smooth (half peal or less). its been running hot in traffic but not overheating runs great if cruising on the highway. Its not bogging down though as you would think with the coolant entering the combustion chamber. it feels like only one or maybe two cylinders are missing but this is erratic not constant. If i slam the pedal it fights me up to speed until i let off the accelerator and let it catch up with my foot. When i looked deeper (Research online) i found that there were also problems with the harmonic balancer counterweight. after reading this I think that it could be the reason for erratic timing issues. if the crank is out of balance then the pistons may be out of time if only for just a moment. not sure what to do. I hope i haven't damaged the engine too much still less than 100K. if i have to replace the intake is there an option for a aluminum swap without too much hassle? would hate to have to keep replacing an intake manifold ever 10K miles. no audible knocking, ticking or whining. please somebody talk to me.